5G Home Internet nightly slow down

I feel like I shouldn't be complaining because compared to everyone else I seem to be a lucky one. But I feel like I'm getting less than someone who is paying less than I am. Context: When I first got my home internet I was elated, 400mbs down/ 60mbs up. Few weeks later my Internet speed goes down. However not like you'd expect. My down speeds is roughly 200 mbs down on a bad and still can cap off at 400. But now my up speed is borderline unusable. About 2-6 mbs and I've even seen it hit 1mbs before. I can't participate in video calls for work, I can't send large files conveniently, and multiplayer gaming is out of the question. The most frustrating part is that my brother, whom I live with, that has his own T-Mobile home internet, got on when they had that $40 a month promo and is getting speeds within the 20-40 range up. So he's paying less and getting better results. It can't possibly be a coverage thing since I can see the tower from my window. Talk to customers service and they just want you to restart over and over. It can't be end of the month throttling because I'm getting this even now with the new billing cycle. Fast download speed, abysmally slow up speed. I have tried everything that others here have suggested so please don't reply with "did you try moving the router." It's in the best spot possible. I really don't know what to do now.