Your code assumes that "3D Survival.exe" exists in the current working directory. You need to provide an absolute path, or a path relative to the working directory.
If you want it to be relative to your executing program, use this:
Path.Combine(Path.GetDirectoryName(Assembly.GetExecutingAssembly().Location), pathToExe);
To get the current working directory just use:
Directory.GetCurrentDirectory();
Your working directory could be different than you think it is, and this will tell you for sure..
To do an absolute path, just put the whole path into Process.Start, or into the StartInfo.FileName