Redmine

Dear all,
I would like to ask you if there is a way to do a backup of Redmine with which I can restore and have the Redmine working again in my synology. As you already know may know, the Redmine in Synology is running through Docker.
I can take backup of the database of MariaDB and the directory which is under docker. But is this enough?
I tried to install some plugins and some of them cause problem to my Redmine and with restoring the directory which is under docker is not enough.
Also, can anyone tell me where are the Redmine system files like CSS?

Thanks in advance
Elias