Https redirect in htaccess after 48h overwriten?

Hi again,

got a problem with my nextcloud installed on a shared webhost.
Yes, I know, it is not the best solution, but works fine for me.
Only thing is, after aprox. 48h my .htaccess gets overwriten and
then the https redirects are gone so the cloud is also available
from http and that is not nice. The nextcloud is in a subdir of the
domain. A friend told me, there should be a switch/button in the
web gui, to turn it on permanently, but I found nothing there.

How can I switch on permanently https redirect for my nextcloud
on a shared webhost php installation?