I have Reboot loop after replacing faulty battery

First thing is to get the phone to tell us why it's rebooting. @flannelist has written our definitive guide to these sort of boot loops, which is called a kernel panic. What you'll want to do is read through the wiki page and use that to locate the latest panic log. Copy and paste or take a screenshot of the first page then come on back and edit your question to add that information.

Based on what it says, we can usually make a pretty good determination as to why your phone is rebooting. It's entirely possible it's completely unrelated to the fixes you've made so far, but we won't know till we see the log.

iPhone Kernel Panics - iFixit

By the way, what was going on with the battery such that you felt the need to replace it? What kind of symptoms were you seeing? How about the screen; why did you replace that?

@jxhnny Ah, yeah, that's a different situation. Try disconnecting the flash/power button cable; that's a common source of reboot problems. With it disconnected, plug it in and it'll power up; if it works you'll need to replace that assembly. iFixit doesn't have a guide for that repair but there's one over at the Nadie Me Llama Gallina site. It's in Spanish but if you use it with the Chrome browser's translation it's quite usable.

Manuales / Apple iPhone Xs / Ignition switch, microphone and flash