Owncloud 9.1.5 mysql connection problem

Hi;
os: ubuntu 16.04
php: 7.0.33
mysql: Ver 14.14 Distrib 5.7.33
When i run with sqlite i get no error. But i change config.php file for mysql i get server say “you must upgrade to owncloud version”. Than try the upgrade owncloud with “occ upgrade” i get this Exception: Updates between multiple major versions and downgrades are unsupported.

You cannot switch from sqlite to mysql by simply editing the config.

but it was working with mysql before. i dont understand how it switch to sqlite. My all users etc. in mysql.