You can check if the firewall is active by running the following command in a terminal:
sudo ufw status
if it is turned off....you can turn it on by typing firewall into the menu......it should only require one single click to turn it on. Once it is turned on ut will automatically turn on each time the pc is either rebooted or started.
Spend some time and secure your browser.
I use Firefox......with Malwarebytes Browser Guard, Ublock origin, and https everywhere. I get them from the add ons area in Firefox menu.
The browser is the no.1 area for malware entry so....make it secure
I have run Linux Mint for around 4 years + with the firewall and those addons with no ill effect. I browse far and wide ....probably a little "wider" and "further" than would be considered safe.
Keep asking questions here....we have a good friendly crowd with a very wide knowledge base.
I also started with Peppermint (approx 4.5 years ago).....it lasted on my PC for a few days and then I gave it the flick. Info was not easy to come by.....it was not what I expected.
I installed Linux Mint (cinnamon desktop) and have never looked back. When I installed the LM (linux mint) version was 17.1...it is now up to 19.2.....but I have stayed at 18.3....because it is bulletproof/suits my needs perfectly.
When they release a version which shows the same or similar attributes as LM18.3, i will move on. I did try 19.2 and was disappointed.
For the time being, 18.3 is supported by the Linux team and the support available both here at linux.org and all over the Internet is outstanding.
When a new OS (operating system) is installed it is a good idea to also install/use Timeshift. It takes a snapshot of that OS....so if something goes south you can easily set it back to where it was before things went wrong.
Are you aware that you can "TRY" any linux distro....without actually installing it ? It will run from a usb stick, uses RAM to do this......and does not affect your hard drive. It will run a little slower than an installed distro, but will also run well enough to give you a really good idea of that particular os/distro.