PokerTracker

Hi,
Is there a way I can delete all my results for a certain limit? Or start a new database just for that limit.

I used to play 50nl a long time ago and am gonna start playing it again but i dnt want any of my old results

Have a look at the menu item Utilities / Database maintenance and options, then Advanced Purge. Make sure you let it make a backup copy of your DB before you do any purging as you cannot retrieve any purged data (unless you still have the hand histories).