In fact, you can delete unnecessary software through root, which can slim down the machine.
Also, you can choose to brush the compressed rom to realize it.
There are also, for example, some people like a lot of beautified Roms. Or a lot of software will inevitably take up a lot of memory. Anyway, not all software will be stored in the card. Like input method?
If you watch it again, you can go to forums more often, and then study, so you can play with your mobile phone.