Confluence server.xml how to permanently save changes in the file?

I have a question about Atlassian Confluence
Does anyone knows how to change configuration in server.xml located under
/opt/atlassian/confluence/conf/
Currently I have this directory mapped
-v /data/var:/var/atlassian/application-data/confluence
Each time when I do some changes and restart container config is gone and this is clear because server.xml is not permanently saved.
The problem is when I try to map second folder
-v /data/opt:/opt/atlassian/confluence
If above is mapped than I cannot start container

Anyone knows how to solve that?

Thanks
Rafal