"Yesterday I was at the restaurant."
Translation:Ayer yo estuve en el restaurante.
It accepted 'Ayer fui al restaurante.' but not 'Ayer fui en el restaurante.' and it lists 'Ayer yo estuve en el restaurante.' for the main answer. Can anyone please explain what is the difference between 'estuve' and 'fui' and why use 'en' with one, but 'a' with the other?