Hi Fiona Nevell
It looks like you still have a module for the "app" or "system" menu on your home page so you should be able to edit it in the module admin page, e.g. here for you:
Hopefully you won't have deleted the whole menu (that should be difficult) but just disconnected it from its module, so in the
Module tab on that edit form set the
Menu (id) field to 42, then click Assign at the bottom.
You can find more info on modules here https://doc.tiki.org/Assigning-Modules
Crikey, that sounds grim! Sorry about that... which browser is this in? Not sure why it should be so totally unusable for you - and sorry the RTM's usually happen in Europe/America friendly times... i guess if you could log in here you could vote for other times, so sounds like we need to get that fixed first. Maybe try the gitter chatroom some time?