OK, need to try and sort things out:
1. Time Machine "device". I suspect you are using Time Machine for your backups, and I can only guess that with your Time Machine "device", in its default configuration, Time Machine runs only at your "direction". Maybe you need to configure Time Machine to run more often. Again, though, given that I have no experience with that device nor Time Machine, maybe someone else can "chime in".
2. Time Machine backups are not bootable, ie, you cannot boot your Mac Mini from a Time Machine backup (no matter what kind of external device you have). To be able to boot your Mac from a backup, you need to use a backup/cloning program like either SuperDuper! (I use it) or Carbon Copy Cloner.
3. The link
https://support.apple.com/en-us/HT206886: I just clicked on it, and it says "Get El Capitan from the App Store" (about half way down). #1 says "Use this link to open the El Capitan page on the App Store:
Get OS X El Capitan.". Just click on "
Get OS X El Capitan.", and that will take to to a page that shows El Capitan V10.11.6 of El Capitan. Click on the Download button, and the download should start. Once it completes, do not let it "run" any further". Quit that "process". The result of this will be a file entitled "Install MacOS El Capitan" inside your Applications folder. Make a copy of it in another location on your machine. To do that:
a. Click on that "Install MacOS El Capitan" file once.
b. Go to the Edit menu, and select Copy.
c. Navigate to another folder/location.
d. Double click that folder, click once inside it, and then select "Paste" from the Edit Menu. The file "Install MacOS El Capitan" will be copied to that location.
I don't understand your statement "I got the button to work and got the message "This version of OS X 10.11 cannot be installed on this computer.". What "button" do you mean? Also from that "El Capitan" link, note that you can install El Capitan on your Mac Mini (within the list of Macs on that link, it says "
Mac mini models from early 2009 or later". Well, you have a late 2012 model like me.
Also, what do mean by "i use a solid state drive"? Is the Solid State Drive (SSD) inside your Mac Mini (like mine)?
Please 1) clarify what I asked above, and 2) try and follow #3 above (about obtaining V10.11.6 of El Capitan). That link worked for me.