It all depends on what you’re gonna try to repair, the most common replacements are screen and battery in my experience, i would look at those reviews and they will be a lot more in depth.
A couple things could be wrong, your battery may need replacing, your power button could be bugged, or you could just be screwed. I recommend closing and opening the lid a couple times and pressing some keys, if that doesn't work open it up see if the battery is inflated, and if it is, replace it, if it isn’t I recommend taking it to a service center. And if your computer smells like smoke its likely fried.
Well this is just a guess, but I think it may have something to do with your speakers, if you did maintenance you could've damaged them, I unfortunately do not have access to a analytics translator though, so if you have a warranty you can take it to apple and they'll be able to tell you.
It sounds like its your screen cables so make sure theres nothing (such as debris, try blowing on the wire and connector) in between the connecter and the wire also make sure the connectors is properly aligned and firmly attached, if that doesn't work you might’ve broke the screen.
Multiple potential issues, bad battery (sometimes it isnt detected as noticed in my experience), overuse, social medias are a burden on your battery, you didnt specify which SE is was so it could be the first gen, if so thats just not a great phone, or potentially a virus or malware, make sure to close your tabs overnight.