Any way to resolve a slightly pixelated video?

I remotely recorded a video (for an art project) of someone using their cell phone. Phone was doing 4K @17278815. The platform that allows me to see a livestream of what I'm getting isn't super hi-res, so I did a brief test video to make sure it was looking good. Test video looked fine.

Started a new recording for the actual shoot, and when I downloaded it (this was all done using the Riverside platform), for whatever reason, THIS video (same lighting conditions, etc) is oh so slightly pixelated. Not too bad but not as good as the test video.

I am completely new to video. Is there some way in Premiere to get it to...fix it a bit? Explain it to me like I'm 5. Thanks!!