Thank you for your answer. I asked because i'm not lifetime-member and don't still have the game. If i buy both things (the game at steam and lifetime-membership here) i would like to use the game with the trainer. Because of that i asked before
Did you look at the readme.txt file that came with it, it usually has tips and the proper way to use an option in it.
Add the trainer manager to your exclusions list in security software/anti-virus and make sure www.cheathappens.com is in your web browser(s) whitelist. Clear the cache and cookies and try it again.