Many False Errors, although Cmake compilation works fine

I have opened a large Cmake project with clion and the compilation and execution works fine.
But for many parts in the code Clion shows a lot of errors and doesnt even recognize some functions (hence no autocompletion for those). I m wondering why compilation and execution works fine, although Clion shows me so many errors.

Would it be possible to upload the project somewhere, so you can check where the problem is?