knack knack

Went to my maternal grandparents' with my mother. On the way we stopped by at a local grocery store, where we got a plastic bag with these words. I don't understand what the third and fourth sentences mean, but it seems that, when shopping, bringing your own bag is encouraged by the whole passage. I don't see why English, not Japanese, is chosen here either.

After having sashimi (slices of raw fish) we went back home early in the evening.