My Mi Max 2 is very slow

[Arjan]

HELP: My Mi Max 2 is very slow

Android 7.1.1 NMF26F
MIUI Global 9.6 Stable 9.6.3.0(NDDMIFD)


Starts itself up again and again,
apps linger (...... does not respond)
Process system does not respond
Android system does not respond
Getting back to factory settings does not help, just lose everything
what to do?