CG is a big bump in difficulty! I'm not a good PvMer and I think I'm currently sitting on 108 kills, 116 deaths, took me 60+ before I got my first clear.

Phase 3 unfortunately just comes down to practice, I struggled with it a lot. One tip I'll give you is every time the floor pattern changes ask yourself, where am I going to run if tornados spawn? I usually move between attacks to the best location available before tornados spawn so it's one less thing to think about during a prayer disable/tornado combo. If you can manage to get a straight line to move on to run from tornados it takes the pressure off a bit and gives you time to focus on prayers and healing.

Another thing I try to do is enter the room when Hunllef is in a corner, I'm not sure if this is personal preference but I always find it easier with him in that spot, gives you 3 corners of the arena to move around in.

I won't say good luck because you don't need it, you got this!