The Backfire mini comes with hobbywing hub motors. At some point, you will need to swap out the PU sleeves. Daniel Kwan made a great video below addressing how to do this with this type of motor. If the inner motor cover comes off with the sleeve don't panic you can slot it back on.
If you ever need to swap out the Mini sleeves or an entire motor here is a guide on how to do so. Please remember to turn the board off before doing this. Thanks for Seed Visual for providing the videos. Please check their channel for more fun contents.
For more general electric skateboard maintenance check out Daniel Kwan's video for how to take care of your board. Remember to regularly inspect all screws on your board and tighten them as necessary.