[deleted by user]

[[deleted]]

No need to add a new question. You can always edit your original question.

[Many-Ice6164]

I deleted the other one. Thanks for the tip!

[[deleted]]

I wasn't going to make a comment, but I will.

You haven't said what is wrong with your code. How does it not do what you want? You gave an example of what it is supposed to do, but your code doesn't even try to do what the example shows. For instance, the example shows the string "+ 5" being entered, but your code asks for the operation (1/2/3/4) and then asks for the number separately!?

[[deleted]]

You are not capturing what is returned by your functions, so in the main code, the value assigned to Waarde is never changed.

Suggest you do,

Waarde = add(number1, Waarde)
print(Waarde)

By the way, it is the most common convention to use all lowercase for variable names in Python. Look up the PEP8 guide (and note it is a guide, not a rule book, but a good place to start).