Cell service and GPS not working.

I have an iPhone 8 plus, and my cell service doesn't work well. It seems to work ok if I am close to the cell tower, but if I am farther away, my phone often says no service, or it has one bar, and nothing works. Other people's phones with the same carrier who is in the same place have working cell service.

Also, the GPS doesn't work well, it says I am in a place half a mile away and doesn't update for a while. This makes it impossible to use for navigation while driving.

My phone was dropped, and the top and right side metal pieces are coming apart near the seam by the main camera. The problems started happening a while after, but this probably has something to do with it. Here is an image of where my phone is coming apart.

If I squeeze the top of my phone (metal part) and the bottom (speaker grille), cell service and GPS start working, but when I stop squeezing, it stops working. Rebooting the phone seems to help sometimes.

What can I do to fix these problems? Is there a replacement cell antenna that I can buy that will solve the issue?