How to start using docker?

Question

Docker

Good afternoon!
Recently I came across such a wonderful thing as Docker. At first glance, the thing is interesting and should make life easier, but so far I can’t understand and scroll through the entire infrastructure in my head when using it. So, at the moment we have:
1. Several web servers (3-4) with nginx+apache-mpm-itk;
2. Several dozen unrelated projects;
3. Dedicated DBMS server (MySQL, Redis, MongoDB).
Storage is planned for the future. Actually, as I see it working at the moment:
1. Several servers running Apache containers. On the servers themselves, a directory with sources is mounted, which lies on the storage system, and the directory with the sources of each project is "thrown" into the container, and the directory for logs is also forwarded. Thus, the containers are identical, the only difference is in the forwarded directories and IP addresses;
2. Nginx is located on two more servers, which balances the load between containers;
3. The DBMS remains as is.
To what extent is this scheme adequate and used in practice? And who is implementing the deployment of sources from Git?