Can someone help me figure out what's wrong with my iPhone?(logo loop)

This problem first started when my iPhone suddenly died for no apparent reason. It was just sitting at my table (the screen was on) and poof. So then I tried to connect it to my computer, to see if it would boot up again or something, but there was no response on the device. So I opened the phone, disconnected and reconnected the battery (I should have plugged it to the wall first, but I didn’t think of that), thinking it would solve my problem. But when I tried to connect it to my pc again, no response. This time, however, I had the idea to plug it to the wall, and then the logo appeared. But it was stuck in a loop. Then I searched the internet for solutions, and it said I needed to do iTunes recovery and backup. Unfortunately, since right now I have no access to my computer which has iTunes installed with all my backups (and won’t have for a few months), I was pretty disappointed and thought there would be no way to fix the phone for a long time. To be honest I don’t think it would work anyway, since the phone is not being detected by the computer I am connecting it to . Since my power button is stuck, I couldn’t try any of the other solutions involving the power button either. So I pretty much gave up and decided to think about it later. However, for some reason, I decided to plug it to the wall again a few hours later, and to my surprise, it booted. And it was working fine, except it would shut down unexpectedly, but it would always boot again when plugged, to the wall or to the pc. I came to discover it was shutting down whenever it bumped. After searching the internet again, apparently the problem was the connector. So I opened the phone again, disconnected the battery, and checked the connector. The connector seemed perfectly fine. Unfortunately, after reconnecting the battery and closing the phone, I got the same problem as before. It would get stuck in the loop again whenever I plugged it. And it never booted again, it’s just now stuck in a loop. I would really like to know what to do now, I don’t know where is the problem. I suspect it’s the connector or the battery, but I’m not sure, so I opened the phone again and took some pictures of both so maybe you can tell me what’s wrong. I’m thinking about buying a power button replacement first so I can troubleshoot it better, should I do that? I don’t really want to go through all that trouble unless absolutely necessary. I also don’t want to buy a new battery unless absolutely necessary.

Also, I don’t know if this is important or not, but 2 months before I had this problem, I replaced the front screen and home button of the iPhone, so maybe I screwed something up. I also know (not 100% sure) that the battery was replaced in 2018, although it’s good to keep in mind that the same guys who replaced the battery also replaced my original (broken) display with a low quality display (which is why I had to replace it).

Sorry for the wall of text, english is not my first language, and I’m really not good at explaining stuff. Anyway, images of the connector and battery, if it’s any help