I haven't used C# so far, so I only heared that C# doesn't have pointers. I'd like to know how C# would handle the following situation best:
an extremely long string that I would mark in C with a few pointers here and there so I could go back to them and add some information. The idea is that I don't want to go trough the whole string to get to these positions but jump right there; I know pointers would handle that pretty well, but if you already have a better idea let me know.
Now how would C# do that without going throgh the string? It might sound pathetic rigth now but this will be a major performance point for my project so I'd like to know if C# is a good choice for it.

C# has pointers - you just have to stick any pointer stuff into an unsafe { } block.