Hallo, Is it possible, that I can add the strings '1' '.' and '2'. I want to add this 3 strings: 1.2 and convert it into a float value and than I want add a float value.
"My problem is"
Your problem is that you have still not understood the nature of a string, and the difference between strings and numerical values.
"I get form the MDU"
What is an "MDU"?
A string is, by definition, for text - in C251, that means ASCII-coded characters.
To do arithmetic, you need numerical values such as int or float.
Standard library functions exist to convert between strings & numerical values - look them up! Alternatively, write your own.