Updated, thanks.
https://www.openstreetmap.org/node/11830861911
In doubt, I’ll settle to restaurant.

There is an uwritten rule that if you are standing at the counter when ordering your food it is "amenity=fast_food" and if you are seated at your table it is "amenity=restaurant".

Another hint in StreetComplete.  You can activate the "Places" layers and from there every existing business becomes clickable and you can change the name and business type yourself.  Always comes handy.