Desperate for help

Good day good people i use an IMAC Desktop 27inch for several years now and don't think will go back to windows I came across some technical issue firstly it started with the blinking folder (?) issue tried to fix it several times after a while it went to the Padlock icon with a text box underneath, so I went to YouTube for some tips I tried still couldn't fix it

one of the Videos I came across I managed to retrieve my Ref NO: and was asked to send to apple support not sure but I visited the website is www.efiunlock.com but the website it's still short down. Please I really need help for am right now at Nigeria and can find any Apple dealer shop so am stranded pls how can You(Apple) help please??

Thanks

Ibrahim Tijjani