diff --git a/src/main/java/edu/kit/typicalc/model/parser/AdditionalInformation.java b/src/main/java/edu/kit/typicalc/model/parser/AdditionalInformation.java
new file mode 100644
index 0000000..c1df3e1
--- /dev/null
+++ b/src/main/java/edu/kit/typicalc/model/parser/AdditionalInformation.java
@@ -0,0 +1,8 @@
+package edu.kit.typicalc.model.parser;
+
+public enum AdditionalInformation {
+    /**
+     * Duplicate VarType after Universal Quantifier.
+     */
+    DUPLICATETYPE
+}
diff --git a/src/main/java/edu/kit/typicalc/model/parser/ExpectedInput.java b/src/main/java/edu/kit/typicalc/model/parser/ExpectedInput.java
index 8fb4556..dcd73ef 100644
--- a/src/main/java/edu/kit/typicalc/model/parser/ExpectedInput.java
+++ b/src/main/java/edu/kit/typicalc/model/parser/ExpectedInput.java
@@ -12,5 +12,9 @@ public enum ExpectedInput {
     /**
      * Any kind of type.
      */
-    TYPE
+    TYPE,
+    /**
+     * // t[0-9]+
+     */
+    VARTYPE
 }
diff --git a/src/main/java/edu/kit/typicalc/model/parser/ParseError.java b/src/main/java/edu/kit/typicalc/model/parser/ParseError.java
index 9cd9d0b..d6664c3 100644
--- a/src/main/java/edu/kit/typicalc/model/parser/ParseError.java
+++ b/src/main/java/edu/kit/typicalc/model/parser/ParseError.java
@@ -62,6 +62,7 @@ public final class ParseError {
     private Optional<Token> cause = Optional.empty();
     private Optional<Collection<Token.TokenType>> needed = Optional.empty();
     private Optional<ExpectedInput> expected = Optional.empty();
+    private Optional<AdditionalInformation> additional = Optional.empty();
     private String term = "";
     private char wrongChar = '\0';
     private char correctChar = '\0';
@@ -93,6 +94,17 @@ public final class ParseError {
         return this;
     }
 
+    /**
+     * Attach additional information to this error.
+     *
+     * @param additional the additional information
+     * @return this object
+     */
+    public ParseError additionalInformation(AdditionalInformation additional) {
+        this.additional = Optional.of(additional);
+        return this;
+    }
+
     /**
      * Set expected token types of this error.
      *
@@ -210,6 +222,13 @@ public final class ParseError {
         return errorType;
     }
 
+    /**
+     * @return the additional information
+     */
+    public Optional<AdditionalInformation> getAdditionalInformation() {
+        return additional;
+    }
+
     protected void setErrorType(ErrorType errorType) {
         this.errorType = Optional.of(errorType);
     }
diff --git a/src/main/java/edu/kit/typicalc/model/parser/TypeAssumptionParser.java b/src/main/java/edu/kit/typicalc/model/parser/TypeAssumptionParser.java
index 701d472..f21b68a 100644
--- a/src/main/java/edu/kit/typicalc/model/parser/TypeAssumptionParser.java
+++ b/src/main/java/edu/kit/typicalc/model/parser/TypeAssumptionParser.java
@@ -10,6 +10,14 @@ import java.util.regex.Matcher;
 import java.util.regex.Pattern;
 /**
  * Parser for type assumptions.
+ * Parses according to the following grammar:
+ *
+ * TypeEnvironment --> ɛ | TypeAbstraction, TypeEnvironment | TypeAbstraction
+ * TypeAbstraction --> Variable | Type
+ * Type --> ∀ VarType.SingleType | SingleType
+ * SingleType --> SimpleType Rest
+ * SimpleType --> Variable | (SingleType)
+ * Rest --> ɛ | -> SingleType
  */
 public class TypeAssumptionParser {
 
@@ -47,14 +55,14 @@ public class TypeAssumptionParser {
     public Result<Map<VarTerm, TypeAbstraction>, ParseError> parse(String assumptions) {
         lexer = new LambdaLexer(
                 cleanAssumptionText(assumptions), ParseError.ErrorType.TYPE_ASSUMPTION_ERROR);
-        return parseTU();
+        return parseTE();
     }
 
     /**
      * parses Type Environment
      * @return if successful, a map of the type assumptions, otherwise an error
      */
-    public Result<Map<VarTerm, TypeAbstraction>, ParseError> parseTU() {
+    public Result<Map<VarTerm, TypeAbstraction>, ParseError> parseTE() {
         HashMap<VarTerm, TypeAbstraction> map = new HashMap<>();
         while (true) {
             Result<Token, ParseError> nextLexerToken = lexer.nextToken();
@@ -115,6 +123,11 @@ public class TypeAssumptionParser {
         return new Result<>(new MapEntry<>(term, result.unwrap()));
     }
 
+
+    /**
+     * Parses a Type
+     * @return if successful a type abstraction, otherwise an error.
+     */
     public Result<TypeAbstraction, ParseError> parseType() {
         Result<Token, ParseError> nextLexerToken = lexer.nextToken();
         if (nextLexerToken.isError()) {
@@ -139,7 +152,8 @@ public class TypeAssumptionParser {
                 String input = currentToken.getText();
                 if (!TYPE_VARIABLE_PATTERN.matcher(input).matches()) {
                     return new Result<>(null,
-                            ParseError.unexpectedToken(currentToken, ParseError.ErrorType.TYPE_ASSUMPTION_ERROR));
+                            ParseError.unexpectedToken(currentToken, ParseError.ErrorType.TYPE_ASSUMPTION_ERROR)
+                                    .expectedInput(ExpectedInput.VARTYPE));
                 }
                 int i = Integer.parseInt(input.substring(1));
                 TypeVariable v = new TypeVariable(TypeVariableKind.USER_INPUT, i);
@@ -148,7 +162,8 @@ public class TypeAssumptionParser {
                 for (TypeVariable var : quantifiedVariables) {
                     if (var.equals(v)) {
                         return new Result<>(null,
-                                ParseError.unexpectedToken(currentToken, ParseError.ErrorType.TYPE_ASSUMPTION_ERROR));
+                                ParseError.unexpectedToken(currentToken, ParseError.ErrorType.TYPE_ASSUMPTION_ERROR)
+                                        .additionalInformation(AdditionalInformation.DUPLICATETYPE));
                     }
                 }
                 quantifiedVariables.add(v);
@@ -190,6 +205,10 @@ public class TypeAssumptionParser {
         return new Result<>(new TypeAbstraction(result.unwrap(), quantifiedVariables));
     }
 
+    /**
+     * parses a single Type
+     * @return if successful a type, otherwise an error
+     */
     public Result<Type, ParseError> parseSingleType() {
 
         Result<Type, ParseError> result = parseSimpleType();
@@ -216,6 +235,10 @@ public class TypeAssumptionParser {
         }
     }
 
+    /**
+     * parses a simple type
+     * @return if successful a type, otherwise an error
+     */
     public Result<Type, ParseError> parseSimpleType() {
         if (currentToken.getType() == Token.TokenType.VARIABLE) {
             Type type = parseLiteral(currentToken.getText());
@@ -244,6 +267,10 @@ public class TypeAssumptionParser {
                 ParseError.ErrorType.TYPE_ASSUMPTION_ERROR).expectedInput(ExpectedInput.TYPE));
     }
 
+    /**
+     * parses the rest of a single type
+     * @return if successful a type or an empty optional, otherwise an error
+     */
     public Result<Optional<Type>, ParseError> parseRest() {
         switch (currentToken.getType()) {
             case ARROW:
diff --git a/src/main/java/edu/kit/typicalc/view/content/errorcontent/ErrorView.java b/src/main/java/edu/kit/typicalc/view/content/errorcontent/ErrorView.java
index 7acf54f..844e62c 100644
--- a/src/main/java/edu/kit/typicalc/view/content/errorcontent/ErrorView.java
+++ b/src/main/java/edu/kit/typicalc/view/content/errorcontent/ErrorView.java
@@ -10,6 +10,7 @@ import com.vaadin.flow.component.html.Pre;
 import com.vaadin.flow.component.orderedlayout.VerticalLayout;
 import com.vaadin.flow.i18n.LocaleChangeEvent;
 import com.vaadin.flow.i18n.LocaleChangeObserver;
+import edu.kit.typicalc.model.parser.AdditionalInformation;
 import edu.kit.typicalc.model.parser.ExpectedInput;
 import edu.kit.typicalc.model.parser.ParseError;
 import edu.kit.typicalc.model.parser.Token;
@@ -130,6 +131,15 @@ public class ErrorView extends VerticalLayout implements LocaleChangeObserver {
                     getTranslation("error.expectedToken", correct))));
         }
 
+        // state more additional information, if available
+        Optional<AdditionalInformation> moreAdditionalInformation = error.getAdditionalInformation();
+        if (moreAdditionalInformation.isPresent()) {
+            AdditionalInformation e = moreAdditionalInformation.get();
+            additionalInformation.add(new Span(new Pre(
+                    getTranslation("error.additionalInformation",
+                            getTranslation("additionalInformation." + e)))));
+        }
+
         return new Div(additionalInformation);
     }
 
diff --git a/src/main/resources/language/translation_de.properties b/src/main/resources/language/translation_de.properties
index a1d5690..7c80e51 100644
--- a/src/main/resources/language/translation_de.properties
+++ b/src/main/resources/language/translation_de.properties
@@ -110,6 +110,7 @@ error.termForError=Term:\u0020
 error.typeAssumptionForError=Typannahme:\u0020
 error.wrongCharacter=Falsches Zeichen:\u0020
 error.expectedToken=Erwartet: {0}
+error.additionalInformation = Information: {0}
 error.hint=Die Grammatiken, die die korrekte Syntax eines Terms und der Typannahmen beschreiben, \
   sind auch über das Info-Symbol zu erreichen.
 tokentype.UNIVERSAL_QUANTIFIER=Allquantor
@@ -128,6 +129,8 @@ tokentype.COLON=:
 tokentype.EQUALS==
 tokentype.ARROW=->
 tokentype.EOF=Ende der Eingabe
+expectedinput.VARTYPE= Variable der Form t[0-9]+
+additionalInformation.DUPLICATETYPE= Duplikat
 expectedinput.TERM=beliebiger Term
 expectedinput.TYPE=beliebiger Typ
 root.or=oder
diff --git a/src/main/resources/language/translation_en.properties b/src/main/resources/language/translation_en.properties
index 5413aa2..904a8e2 100644
--- a/src/main/resources/language/translation_en.properties
+++ b/src/main/resources/language/translation_en.properties
@@ -102,6 +102,7 @@ error.wrongCharacter=Wrong character:\u0020
 error.termForError=Term:\u0020
 error.typeAssumptionForError=Type assumption:\u0020
 error.expectedToken=Expected: {0}
+error.additionalInformation = Information: {0}
 error.hint=The grammars describing the correct syntax of a term or a type assumption can also be reached \
   via the info icon.
 tokentype.UNIVERSAL_QUANTIFIER=universal quantifier
@@ -120,6 +121,8 @@ tokentype.COLON=:
 tokentype.EQUALS==
 tokentype.ARROW=->
 tokentype.EOF=End of input
+additionalInformation.DUPLICATETYPE= Duplicate
+expectedinput.VARTYPE= Variable of the form t[0-9]+
 expectedinput.TERM=any lambda term
 expectedinput.TYPE=any type
 root.or=or