As an SEO you're obliged to say translate all the folder names.

If you want to optimize your site for search engines, it is strongly recommended to use keywords in the Urls of the pages you'd like to see in the SERPs ; Its not compulsory, though, and with non-competitive terms you may get good rankings without it. A lot of sites have urls like mysite.com/index.php?page=123 and still rank well

A German site has German keywords obviously and you should have these words in your Url if you want an optimized site

If you're saying that technical reasons you can't do this, you'll have to make extra efforts elsewhere

Make sure that you have a fully translated breadcrumbs and navigation menus ... but if you can do this you shouldn't really be that far off translating the urls

• Neil