How to fix it

first of all ARE YOU KIDDING ME?!?!

why can't people understand UNPLUG !

anyway you need to clean it off is it's only liquid i preffer this method:

unplug and take the battery out

get some alcohol (rubbing alcohol, ethanol whaever you have on hand and make sure it dosen't have and inpurities)

DON"T USE TAP WATER!

take your device appart (you can do it without but it's risky...you can't lose much right now...)

dip every single component in alcohol and try to clean it of, alkohol replaces water (kind of) and solves many compounds that water can't solve and evaporates far quicker than water

try multiple times with the display (it may be hard to do)

take some brush and clean anything you can....anyhow,

you said that the button's don't work so clean of that button contacts really good

after scraping and brushing and whatever you do i preffer to take new alcohol and dip and clean it again than let it dry (alcohol is highly flammable so be carefull (oven is bad place to start))

after it dryes reassemble your device and try to pover it on if something kinda works than try to clean it off again and if it just dosen't work then we need to find other way

btw. if you open your device try to spot some damages and other stuff that look suspicious

if anything works then you'r pretty much done if something sosen't work then let me know (and post some photos)

hit helped it i was helpfull