add and correct mysql info

README.md

@@ -33,11 +33,18 @@ docker-compose exec --user www-data app php occ
 ## Datenbank
 MySQL import
 ```
-docker exec -i nextcloud-db mysql -uroot -pnextcloud nextcloud < SQLFILE.sql
+docker exec -i nextcloud-db mysql -uroot -p nextcloud < SQLFILE.sql
 ```
 MySQL Dump
 ```
-mysqldump -u root -pnextcloud nextcloud > SQLFILE.sql
+mysqldump -uroot -pnextcloud nextcloud > SQLFILE.sql
 ```
 
+**db.env**:
+```MYSQL_PASSWORD=${MYSQL_PASSWORD}
+MYSQL_DATABASE=${MYSQL_DATABASE}
+MYSQL_USER=${MYSQL_USER}```
+
+(change variables)
+
 ## Backup