multi language - each in its own folder?
"there is no 'tab' above an wysiwyg field under the very same article where i can switch between languages and fill in the corresponding content on the very same admin-page, right?"


Actually, there is (sort of). It's not a tab per se, but you can switch between the different versions of each entry as you are editing them.



So you would add all of your entries in English first, then circle back and adjust the content for each entry in German.

And as you mentioned, there is a Site Switcher plugin (disclaimer, I am the author) to let you easily switch between languages while staying on the same page.