I have found this, could I try to update with _all?
Yes, you can do it.
there is a problem: during the installation (dpkg -i deb_all) after unpackage and during “Setting up”, server lost connection and now I dont have “webmin” at all
log:
2020-01-15 14:24:55 upgrade webmin:all 1.940-2 1.941
2020-01-15 14:24:55 status half-configured webmin:all 1.940-2
2020-01-15 14:24:55 status unpacked webmin:all 1.940-2
2020-01-15 14:24:55 status half-installed webmin:all 1.940-2
2020-01-15 14:27:34 status triggers-pending systemd:amd64 215-17+deb8u13
2020-01-15 14:27:50 status half-installed webmin:all 1.940-2
2020-01-15 14:27:50 status unpacked webmin:all 1.941
2020-01-15 14:27:51 status unpacked webmin:all 1.941
2020-01-15 14:27:51 configure webmin:all 1.941 1.941
2020-01-15 14:27:51 status unpacked webmin:all 1.941
2020-01-15 14:27:51 status unpacked webmin:all 1.941
2020-01-15 14:27:51 status unpacked webmin:all 1.941
2020-01-15 14:27:51 status half-configured webmin:all 1.941
then stopped
Now I have
Webmin version 1.941
but I dont have webmin package
However, now let’s encrypt works
should I update also usermin? (“summary” tells me that is outdated)
edit:
I installed usermin and worked. Should I install also usermin-webmail_1.790_all.deb?
I dont have this package
for now I have installed a certificate and worked
Should I install also usermin-webmail_1.790_all.deb?
No!
Nice, lucky me that didnt do it 
However why not? Is only for whom had some email stuff?