Pitting advice?

I dont know why but pitting is the hardest thing in this game for me, i can be in a podium position for the 1st half and soon as the mandatory pit opens i pretty much lose the whole race.

I was in P2 and pitted in the box at the exact same time as the leader and he left the pit and i still had 30 seconds of lock out before i could leave and when i was finally out i was in dead last and spend the past half the race fighting my way up mid tier. I dont understand why im so bad a pitting or what im not getting right all i know is if im on podium and pit im coming out in last place everytime, i hate the pits and it ruins my day lmao

Any advice?