modify game items, cars, background, etc.

Hello i’m brecht I have a youtube channel that is focused on the game from mattel : hot wheels race off and I’m looking for a game developer that could modify the game from me on a steady basis the things i would like to change are the cars. Make them look different other colors and complete other reskins so they are different maybe create real life cars into the game (for example the tesla truck) maybe change the background of the game for seasons like winter and make it snow that sort of things This person on youtube is doing the exact same thing changing the cars from the game into other cars from other games Here are some examples [login to view URL] [login to view URL] [login to view URL] is this possible to do? and we only have the APK file no source code (but this youtube person doesn't have it either) And how much would it cost me to do 5-10 changed cars per month