How to sync 2 separate ubuntu servers?

Question

MySQL

Hello gentlemen,
please help me figure out how best to implement / solve the following problem.
Let's say we have 2 servers - live / production and dev, each has Apache configured differently for domains and subdomains. It is quite obvious that on live we have different domains for different sites - on the dev one domain with a bunch of subdomains for the same sites.
Actually the task: how to properly set up synchronization between these two cats on ubuntu. mysql databases and project files. Manually or scripts.
I have read so many different bourgeois sites and the word deploy has appeared in my everyday life. If I understand correctly, this is just the process of pouring from dev to production.
I understand with my brain that this can be done periodically by hand (as, for example, in the case of a database - exported from live - deployed to dev) well, files can be passed through git (have not yet entered deeply). The dev server in my case is the base, and the production is just a place to spill, right?
They write what can be poured into production through deb packages, you can do export import with a bash script. Well, or as I understand it, you can use a ready-made solution like capistrano.
Actually, having read all this on the Internet, I realized that I simply lack systematized knowledge about the structure, construction methodology and technologies, etc. Totally confused :(
Help build an algorithm / knowledge system that you need to have / what you need to study before climbing into this steppe + what is better to read + what you need to learn catastrophically, and finally, how to solve your problem.
Catastrophically I want to understand, but mired in very superficial knowledge. Please help :(