How to make mac mini server more secure to access?

I just got a handdown 2012 mac mini running macOS Mojave and I wanted to turn it into a server to use for storing files and as a remote time machine that I can access regardless of what network I'm using. I think I can achinve all this by messing with the share setting in system preferences without downloading any extra software, but I didn't find it very secure.  I plan to access the server using a mac pro and a windows 10 laptop so I'm trying to find a salution that will make it secure and not restrict me to accessing it from a single operating system.

Is there a way to make the mac mini server secure. For example, when I access the server I have to use my apple accounts 2 factor authenication, or make it so that the server will reject any attemps to access the server from any computer that are not my specifed devices devices or input a random generated string that is texted/emailed to myself only? Is this possible? How can I achieve this security?