Phone not charging

I have an iPhone 11 and the other day it was dying so I put it on the charger but I had to plug it out a few times because i needed it so I coulldnt leave it plugged in but when it died I let it sit and charge, so when it finally turned on an error message or emergency type of notification popped up and it said “can’t charge because it’s wet, it will take a few hours to dry, keeping it plugged in can damage ur phone” but when I went to plug it out the first time it had some weird black residue on the charger, I finally got it to sit and charge, and it didn’t fall in water or was around water either so I didn’t understand that, and now when I’m charging my phone I have to hold all chargers a certain way or it won’t work and when it does it charges a little slow as well.. I need advice as to what I should do.