What could be wrong with my Phone?

Hi y’all. In 2022 I accidentally got water into my phone. I didn’t even realize I did until my phone shut off and I thought It died. I regret doing this, but I plugged up my phone and possibly fried some circuits. I found the old phone and wondered if all of the circuits were finally dry. I plugged it in and it turns on but it Does not boot completely. The screen turns on. And the Apple logo appears but then after minute or 2 it goes into “dead mode” where it says the iPhone is dead but is currently charging. I don’t need to repair it. But I want to go into a career of tech repair and I feel like this would be a good project. If you have any idea what is happening so I could focus on that or just have any general knowledge I would really appreciate it!