Problem 1:
So I have the anker power case for iphone 6 is it okay to leave it charging over night and my iphone is inside the case?
Problem 2:
My iphone has battery problems it drains really fast because it had a swimming history hahaah thats why my case cannot fully charge my iphone. Will this affect my anker power case battery life too? but the case did not get wet that time
if the battery remains warm after it is fully charged it is not a good idea to leave it connected to the electricity current
It is generally fine to leave something on the charger. It will turn off after it gets to 100%, although doing this will lower the longevity of the battery because it will be constantly filling back up to 100%. As far as I know being wet would not affect battery life. Being old would on the other hand, so you might want to get a battery replacement here: https://support.apple.com/iphone/repair/battery-power