I don't know if I'm improving, regressing or just can't tell

I used to play chess as a teensy kid (not dedicatedly or anything, just for fun) and my main strategy was always just counting on the stupidity of my opponent. After that, everyone who played with me grew up and moved, and by nature I'm not someone who sticks to things so I just stopped playing at all. I'm not consistent at all. I just occasionally played online, once in a blue moon. 
Quite randomly, I signed up for a chess competition (mostly amateurs, not a huge deal) thinking it'd be as easy as before. However, it seems people actually progress and I'm still playing at the level of a ten year old. So I have about 6 days to the competition and it's a matter of the ego. I've noted my weaknesses: I'm horrendous at puzzles (I drag a checkmate out really long), and I can't focus on multiple things at once, which is just about the worst quality you can have while playing. I keep forgetting and losing track of things (I also have adhd which i do not medicate). I'm usually good at picking up just about anything new, but this learning curve is hurting me a bit. No backing out, though. I'm convinced I'm somehow thinking wrong while playing. I'm an absolute novice, so please enlighten me on what's in my blind spot. I try to watch videos but I give up half way. What do you suggest is the best way to start, practice and think while playing?

Yeah, I'm doing that. Playing coach and my accuracy has gone from 60 to 80 but I still don't feel great about it. There's a certain,, method? that I'm missing?

Six days isn't enough time to improve your chess by very much. It takes time to internalize what you learn. And according to your chess.com rapid score, you are starting at 117. That puts you in the bottom 3% of players. I'd still do the tournament because it will be a good experience regardless. But if you are serious about chess improvement it's going to take months and years of work. Not something you can do in a few days.