Thanks, Vidan. :3
@ Leorgathar - Ah, I see. Polish is a hard language to learn. I'm impressed with your knowlege anyway.
"Mój kolega" means literally "my friend/buddy" but it's only corect in sentence like "This is my friend" - "To jest mój kolega" (when talking about him, nominative). If you want to talk to your friend you use "kolego" (e.g. "Cześć, kolego" - "Hi, buddy" - vocative).
"Kolega" is male and "kolega" female. I wouldn't want to learn Polish if it wasn't my native language. xD
BTW. You can pretty much speak Polish without declensions and be understood. It just sounds really weird and... feral?