PLEASE HELP ME. Everytime I compound clips in capcut it changes the resolution of my video by adding the black strips on each side to the actual video

So when it's time for me to crop the video I actually lose resolution. Each individual clip is the same resolution and when I check the player, only the video is selected (white square/rectangle) but as soon as I compound them the black strips get included in the square. I'm losing my mind. Can anyone help.