PokerTracker

i downloaded the handhistory file unzipped it and they were successfully imported but i somehow cannot find any tournaments ive played on ggpoker, while pstars works

Have you selected the correct active player for the report? In other words have you selected the 'Hero' GGPoker player instead of your PokerStars player for the reports?

Guide: Changing the Active Player

If you are using the correct player make sure there are no filters active that would prevent the data from appearing otherwise please attach a screenshot of your entire PokerTracker 4 report window either here or privately in a Support Ticket.