after searching a lot I found cloudlist
a long time ago. However it had some problems with syncing. Sometimes things I added messed up my gf's phone and it just never stopped messing up. OurGroceries seem to support what I need: An easy list with categories. Categories help me find groceries that is close to each other in the store. E.g. Coca-Cola is close to Pepsi Max etc. By just doing alphabetically you end up going back and forward in the store, spending too much time finding stuff. So you gotta use categories. E.g. Wunderlist does not support categories.
I have a list of 293 items now sorted within 13 categories (a lot end up uncategorized as they are..well.. their own category). but most is categorized.
The only problem with OurGroceries is that when you incorrectly press one of the items they disappear very fast. So you don't notice which item you pressed.