About lunch, they usually start at 14:00. The restaurants have "menu del dia", this is perfect because in this menu, you can find everything. You can have starter, main plate, drink and dessert, this is the cheapest way to eat lunch in a good way! For sure if you want to eat in a perfect way other wise you can have some snack all around. For "menu del dia" check around, so many restaurants have this and all of them have different options and different prices. Be relax and find the best option.
About dinner, they eat so late! First when I was there, I couldn't believe. They are eating around 22:00! May be in your country it is usual, but for me it is strange. Also the strange thing is, the restaurant kitchen is closing around 00:00. I remember, when we were late to go restaurant or bar, we were so stressful not to find something to eat.
The dinner in Barcelona with my family in Taller de Tapas!
I wanted to write these info in order to help people about hours in restaurants because really if you don't have any idea, it can be so stressful. It happened to me!