Roblox DiagonalFieldOfView cuts the camera sides so that small devices can't see?

I have a big problem that I have no IDEA how to solve

The problem is that I can't get my camera to get every single part in it in every single type of device sizes

I have found that it has something to do with DiagonalFieldOfView that cuts the camera and cuts some pieces of the Camera if the screen is too small.

I have also noticed changing the FieldOfView messes with the DiagonalFieldOfView also

I have a Camera with my characters model at the near edge of the screen. I made the Camera fit on my laptop which I thought was the end of it until I played on other devices and scaled and made my roblox window smaller.

Then it either got cut off or it collided with the GUI I put next to my character model.

This is a SHOP GUI that I have and it uses a GUI and camera manipulation The GUI is on the left side of the screen and it is perfectly fine

But the Character which I positioned using the Camera to be right next to the GUI changes.

As the DiagonalFieldOfView changes.

My guess is that the answer will be something related to the DiagonalFieldOfView.

and if the answer is about the DiagonalFieldOfView

How would I do the math and make the DiagonalFieldOfView fit on every single screen to return it

One solution attempt I have tried was making the DiagonalFieldOfView the same for me it was 130

But then I realized what about reverting the DiagonalFieldOfView after the player closes the shop how do I know which number to revert it to.