iPhone 6 plus keep rebooting while trying to restore

Hello,

Here’s the story, my mom iPhone 6 plus was glitching out from screen problems. I managed to fix the problem by placing something above the LCD cables to the iPhone when screwing in. So now that was the iPhone 6 plus was working once again, I decide to give it to my mom, however the iPhone was glitchy, and slow. I realize it was probably because of the old battery which was at seventy percent health, so I decided to help her change it. I order a new battery replacement, and everything went smoothly when I repaired the iPhone battery. However my problem started when the iPhone started to repeatedly reboot itself over, and over whilst being stuck in the logo screen. I went on YouTube for help to no avail. Left with no further options, I decide to send the iPhone into recovery mode. I decided to restore, and update the iPhone. Here I started to noticed some problems. While restore the iPhone, it kept disconnecting from the update. I checked to make sure my iTunes was up to date, and changed my USB cables connecting to my iPhone. I realize It wasn’t my computer fault, so I decided to download the IOS update, and upload it instead. That however did not work either as when the iPhone started to update, it just straight up reboots itself kicking itself out of recovery. I searched everywhere on the internet for help, but there was non. I found some article where it lead me to downloads some software that claims to solve these particular problems, however it would require me to pay. I have no clue rather, or not it work so I decided to comment this message on the forum from you tech expert for help. I would really appreciate anything. Thank you for reading this far!