Hi Eric! Thanks a lot. This indeed was the problem, probably so basic for you guys in this community. The extension that causing troubles was AdBlock 2.67.0, and indeed as you suggested after I disabled it, my Facebook worked again as normal. I just wonder why now, considering I used that extension for 2 years already.
Also I do have extension Adblock Plus installed, but that one is still active and yet all the rest seems normal. Question: you said to delete them, you recommend for me to get rid of them for good? Aren't they of any real use? I am just concern of pop up stuff that can be open or programs that download themselves (I just had it, fake flash thing that it was difficult to remove once I realized it got into my computer) which only happened to me once I had this extensions disabled. So again, would you recommend to delete them then? (by delete them I understand to uninstall them - on Safari> Preferences> Extensions there is a button to uninstall ...).
Thank you very much!
PS. I am not fully sure but due to that flash thing that got into my computer I might have/had a virus or malware. How can I know for real if its out of my computer, or how can I get rid of it. In case you know/can help on that one too.