Welcome back!
I’m sorry to hear you’re not having a great start.
Is this your character here, on Madoran? https://worldofwarcraft.blizzard.com/en-us/character/us/madoran/jolena/
If so, your main problem is that your gear is very low for level 71. You may not be up to speed on the rotation, but with that gear even a very polished performance of the spec would feel slow.
I see you have a lot of the Mountainsage pieces at ilevel 360. Did you accept a “Gear Update” when you returned? Something like that? Even so, you must have levelled fast without getting many upgraded pieces. I would like a level 71 to be wearing about 450s, or getting towards that, and there definitely is a gear-trap at the start of TWW where it’s not possible to get a lot of new pieces quickly.
You can check the Auction House for upgrades, but levelling gear is absurdly expensive this expansion, so you may not find much.
While you are there, pick up a stack of potions! Algari Healing Potions are this expansion’s healpots.
So what can you do? Did you level through Dragonflight last year? You seem to have the achieves. Do the World Quests there offer any upgrades? The Dreamsurge event, which should be on the map in one of the four zones, offers Dreambound 454 gear for 100 Dreamsurge Coalescence, which you can get by flying through the green orbs you see in various places.
If you would rather stop for a bit and grind some gear before continuing, you can do that in DF.
Other than that, I’m not sure I can offer any quick advice to help. I play Frost myself, but even being familiar with Frost, I think I would struggle with that gear disadvantage.
As Arcane, the trick is to use the downtime between mobs to use Evocation, while keeping your Arcane Charges up as much as possible. Blast one mob, Evocate if needed, and blast another. It’s a fairly mechanical process. Letting your Arcane Charges drop means that you have to build them up again, and as a squishy clothie, you may not have the time for that.
P.S. as an afterthought
If you accepted a Gear Update, was the gear you had originally BETTER than the Mountainsage pieces the Gear Update gave you, by any chance? Did the Gear Update actually downgrade your gear?
You will have received your original gear in the mail. Worth checking.
If you vendored that gear, you can get it back through Item Restoration
https://us.battle.net/support/en/restoration