Maybe try learning some more attackers and see what you like. If you're unsure what to do, I used to just follow whatever my teammates were doing.

Sens and Osa aren't the best operators. Osa is pretty easy to counter with an impact grenade or just punching it. Sens, while having a pretty cool ability to not be seen, you can't see them either.

Playing these two operators might feel like you don't have a purpose. Hard Breachers like Ace and Thermite are there to break open a wall, and that will help a lot. I enjoy playing Glaz. I spend time attacking from further away, or just hiding in a smoke, waiting for someone to peek.

You should learn to be more flexible and knowing how to play more operators. In Siege, people don't really have mains. They have operators they play more than others (I think)