Im lvl 13 or so and i started this mission and entered the tomb and im pretty far into it i think. Im in a room with five ghost and its just me and aela and im getting absolutely demolished by these guys. So i was wondering if theres a easy way to destroy ghost or if i can just leave this mission and come back later when im a higher lvl. Another question is if i decide to leave will my progress in the dungeon be saved or will i have to redo the fights?

Your progress in the dungeon should remain intact. If you ever run into a hard fight, you might want to try turning down the difficulty for it as you can do that very swiftly through the Options-menu.

I didnt even know there was a dificulty setting. Thank you.

Yea, always be willing to turn down the difficulty, there's no penalty whatsoever and you can do it on the fly.

Most missions aren't that time sensitive from what I've played so you should be able to just leave & come back to it later, or just load up the autosave of you walking into that area & walk off to just avoid it until later.