ok perfect and it worked.
For others, what I did (suggested by wfasa: thank you!)
1 - checked with my provider if json was indeed active (it turned out it wasn't)
2 - in my provider's cpanel -> options-> PHP I went to the 'select PHP version' and settings, activated PHP 5.6 and activated the json module to load.
site is now up and running, WITH Wordfence ON and everyone is happy. It really just took 2 clicks once I knew what to do :-)
NOTE: remember to activate wordfence again (admin, plugins), if you deactivated it through renaming the folder with ftp.