New player PVE help

Hi, I am pretty new to the game, i have only completed the campaign and played like 5 pvp games. I'm really hooked with all the badass armor customizations and the gameplay. However I see that the majority are playing pve and I want to try that too. I tried operations and it felt like im just replaying campaign, so tried siege.. but boy oh boy either I suck at this game or the game is tough. I keep losing at the 3rd wave or before and there are no rewards from it so it feels annoying. Can anyone guide me on where to start?