How can I make my game fit depending on the mobile device?
Mobile devices do not have a standard resolution, nor even a standard aspect ratio.
Your options are going to be either forcing the aspect resolution to stay the same and have black bars on each side that is out of ratio (by setting “No changes to game size” in your project properties), or you will need to design your game to allow for the resolution to be larger or smaller (by selecting one of the “adjust size” options).
A good post here explains some of the options: [Solved] Screen resolution - #2 by JoseMoreno. Hope this helps.
Please note that there are numerous threads on the forums with potential solutions to this, so I’m going to close this thread out. If you didn’t previously, please ensure you search for an answer before posting a new thread.