au restaurant - French
al restaurante - Spanish
at a restaurant = in einem Restaurant
You say "you arrived at the restaurant." The preposition "at" is used to show the location where you arrived.
restaurant
restaurant français
Mon restaurant (pronounce mon rest-oh-ron)
"In dem deutschen Restaurant"
un restaurant (masc.)
le restaurant délicieux
le meilleur restaurant
Un restaurant francais.
"aller au restaurant"
il / elle a un restaurant