Is it possible to change the nextcloud login theme without it being overwritten on update?

As the subject says.
If I change theming files according to the nextcloud documentation will they survive an update?

version: 4.4
patchlevel: 2
erratalevel: 328

An own theme will be overwritten indeed. The changes done in Settings → Admin → Theming will stay.

Thanks blizzz
I’ll stick to the built in abilities.