I used go SMS before and now I feel that the response is too slow, so I uninstalled it. But why the built-in SMS is gone? How can I get it back?

Search online for an official ROM for your mobile phone system, then open it as a decompressed package, enter system\app, and find the message. apk (may not be called this name), drag it out directly, put it into the phone, use RE file management to put it into system\app, shut down and restart, and it will appear

You can also flash the phone directly