Make sure the db_host entry in local/config/database.inc.php points to the correct server (hostname or IP).
Also, searching the forum for (HY000/2002): Connection refused may reveal relevant topics.

@naser, did you not mount a volume to your container to store config information? That can be edited outside the container, but chances are this is going to keep happening unless you are familiar with your docker network configuration. If you didn't specify a mounted volume it should still create one which can be accessed from outside, but easiest to access from inside. You can use a docker commend to ender the container from your shell, or in Portainer go to the container and view the ">_ Console"

Maybe there are too many pictures, the master did not update, and finally updated the theme to fix it