If you have files which you don't want to commit to repository, you can add entries to .gitignore file and these files won't be tracked any more.
You can add entry to .gitignore file with echo command:
echo csharp/Presentation/Presentation.suo >> .gitignore
If .gitignore file is not presented in your root directory of the project, you must create it.
The .gitignore file should be in your repository, so that changes to it can be merged and so on.