Never heard of Robinlook in southern Germany. I would have said the other large chain besides Fielmann is Apollo (known as Pearle in another European countries).

++ for fielmann, I’ve used them in Poland a couple of times (so possibly they are in more countries as well). Good quality and a decent price. Note they have a lot of options, also including more “designer” frames, which are getting expensive. Their brand frames are good quality though if you can find some that you like.

fielmann is bad if you want to reasonably thin glasses with myopia north of -6.