I got my iPhone to turn on again. Is it safe to use?

So 3 months back my iPhone 6 had fell in water and was water damaged. The phone had shutoff a couple minutes after being taken out of the water and I had disassembled it to let it air dry for a couple of days. After I had let it air dry, I had turned the phone back on and it was working normally with some screen damage due to the water. A week went by and it suddenly stopped working and turned off. I went to a phone store to see what was wrong with it and a worker there had said “it shorted out and he couldn’t fix it.” After that I lost hope, and went back home and left the phone in a drawer for a month or 2. Yesterday Out of curiosity I got the phone and plugged my charger into it and it turned on. I was shocked. After all this, is this phone still safe to use?