[Topic title amended. Your problem is no more urgent than anyone else's.]
I was trying to install the polylang plugin for the possibility to translate the content on a web page. The result was a blank page with the following message.
Fatal error: Call to undefined function get_current_screen() in /home/35/w70307/ensemble96/wp-content/plugins/polylang/include/admin-base.php on line 58
I can still access the webpage, but I'm unable to get to the dashboard to edit my page. I know that many others haved had similar types of problems, and i've tried to log on to a so-called ftp server through two different ftp clients, but when these clients (Cyberduck and FileZilla) ask for my wp-login information, they also want a number of a port, which i don't know, as I'm not familiar with coding at all.
Any advise on how to fix this mess made by a guy who thought he knew anything about net-publishing (aka me) would be very highly appreciated!