Can't upload Sketches to my Arduino

If i try to upload Sketches to the Arduino(Leonardo) it says:

avrdude: ser_open(): can't open device "\.\COM4´C?0>?A?Ðít'T(üít'8": the system cannot find the file specified

the strange letters after COM4 are changing always

Strange. Corrupted system or virus?

I dont’ think so since i run a virus programm and erverything else on the computer works fine

It looks for me like the end of string is missing behind \.\COM4. Maybe some problem with the IDE during command assembling. Anyway, did you try to download and use a fresh copy of Arduino IDE?

Yeah i tried a reinstall 3 times

So try another PC or in virtual machine. I don’t think it is problem with Leonardo. You can try to upload sketch directly from command line. Just switch on verbose output in the IDE, find the command in the log, correct it and use it. There is also listed folder with all data include HEX file, which is compiled sketch.
BTW, which OS and Arduino IDE version are you using?