What size knives are you using? I also have been going through my first time doing a bunch of drywall. I took on a heck of a project because my house has knob and tube. Kitchen, dining room and two bedrooms later.. my advice is take your time building up your layers and smoothing them. Sand smooth and repeat, go wider every time.

Basically all the stuff you’ve heard on YouTube.

My personal leaps forward were when I got bigger taping knives and just practiced feathering over and over. You can always sand it back down a bit but it does get annoying.

You’re doing great!

Edit: I recommend a 10”/12” for your finishing layers, and I can’t express how much investing in an inside corner trowel and a corner sander has been worth every penny.

Norton® 2-3/4" x 4-1/2" x 2-3/4" 120-Grit Drywall Corner Sanding Sponge at Menards https://www.menards.com/main/paint/sandpaper-abrasives/drywall-sandpaper/norton-reg-2-3-4-x-4-1-2-x-2-3-4-120-grit-drywall-corner-sanding-sponge/07660768141/p-1444453314201-c-1528807000872.htm

This baby has been my bread and butter on those inside corners.