Trouble with how game is being displayed on mobile

Hi everyone! Hope all is well. I am currently learning how to develop a mobile game and I had finished my first basic version that was playable enough for the app store so I decided to build and run my game. I had been using unity editor to play in 16;8 ratio, and that has been working fine which I built my game around and looks good, however the build and run and playing the app on my phone it is in a much larger resolution and the game is pretty much all over the place.

Is there anyway I can fix this easily? Or do I just resize and make everything fit a larger resolution and see if that will look better? I am new to this so any help would be greatly appreciated!

Thank you