Thanks for the answer!
The folders are there and seem unchanged.
I had made a backup using “backup guard”, but I cannot access it. Under plugins where it should be, WP just says “You do not appear to have any plugins available at this time.”
Regarding the permalinks I checked the .htaccess and it does contain the code WP suggests.
Still the link structure is missing and the website doesn’t show up. And on the WP panel neither themes nor plugins can be found (nor even the standart WP themes). The pages and their content can still be found and edited in WP. And in WP their permalinks are the same as before, but outside WP they don’t show up.
Any more ideas?
Many thanks.