First of all, dash attack to up+b doesn't work. Just don't use dash attack.
You played 100% aggressive. Sometime's you have to bait your opponent with wavedashing in and out or wavelanding around platforms. Don't just blindly rush your opponent. You will get baited and punished if that is all you do.
From my first look it seems like you are still somewhat uncomfortable with Luigi's movement. I saw you dodge shield and roll at weird times when you were getting pressured. Your recovery also seemed much more panicked than precise.
Your play is a classic example of someone who worked on the fundamentals enough to be proficient with them, but doesn't seem to have the experience necessary to developer good game sense and use those techniques to their full potential. I noticed you did things like double jump on stage (makes you a LOT easier to edge guard if you get caught), approach Marth from above, and missed sweet spots and some other stuff.
Unfortunately a lot of this stuff comes with just playing the game more so just keep at it.
Your wavedashing when you weren't pressured was pretty good. You are aware of Luigi's attacks and priorities which is really useful.
Honestly, the best advice I can give you is play more and try and panic less when you are pressured.
But here's a video. Some pointers would be much appreciated and ill try to get a better quality one soon.