Dungeon Combat help: Single Encounters take whole sessions.

[Madeiner]

How can I streamline dungeon combat so that we aren't spending months on end to get through a single level of a dungeon?

This dungeon I'm building is intended to give the players two character levels (Minimum) and a mythic tier... Currently, they're all Tier 1 level 8 characters.

((This is a pathfinder game))

I've been in that boat.
I tried a lot of different solutions. I even spent a couple of sessions noting down timing for everything we did.
In the end, we switched to 5e as it was basically the only solution that could cut times drastically.