The bottom-line: Macs can get Malware or in some cases, ransomware. Through no fault of yours, it may sneak into your web browser as a pop-up. A favorite way is through Facebook, if you've been re-directed when on your browser or you see a pop-up asking for money or telling you that you're infected, you've probably have a Malware. BUT -- the Mac Guy can clean it, and show you how to keep malware off your Mac.
The Mac Guy, LLC can help if this seems overwhelming; call, text or email. My contact information is on the left.