What's wrong with my iphone 6?? (water damage)

I'm new to the forums so sorry if this is in the wrong section or something. I have an iPhone 6 that I dropped in the toilet a week ago. It worked off and on, now it's been 2-3 days that it hasn't been working (long enough that I don't think it's magically going to start working again). If I plug it into my computer it'll make the sound like it's connected, but nothing shows on the screen. The last time I saw anything on the screen was briefly last night, the white apple logo came on once but then it faded quickly, with a purplish line on the screen. That's the only thing I've seen on the screen over the past 3 days, other than sometimes the screen would appear "on"/lit up but be a very dark bluish/black color. So I'm guessing maybe I'll need to get the LCD screen replaced, although something else I read said that I would need to get the battery replaced. Can I go to a local repair place and just be like "I don't know what's wrong with it but I need it fixed"? That seems a costly method to go through (what if they don't know what's wrong with it either?).
I've tried a couple things people suggested on the internet such as making sure the ribbon cables inside the cord are still connected.
The other weird thing is when all this started happening, I was trying to get the screen to come back on so I was holding down the home and power buttons and I eventually put it into DFU mode. I was able to get it out of DFU mode before, then started using my phone again, but now it's stuck in DFU mode. If I try to restore it in iTunes, it comes up with an error code (I don't remember the first code that happened, but the most recent time was 4005). I also downloaded two programs (fonepaw and phonerescue) and both of them get stuck if I use them to try to get it out of DFU mode.

I'll be eternally grateful for any help!