I have some small flying insects in my house. Could these be termites?

Is the entire house brick and concrete or is there wood floor joists, is there wood frame walls behind the brick or do you just see the brick inside and out?

If the roof wood or concrete ?

If there is wood and I would say you have a lot of wood in the house, of course you can have termites

Aren't termites invisible to the naked eye?

Absolutely NOT. Termites are very visible and at certain times of the year, they swarm. They are not tiny but not huge either... a little smaller than a house fly with a tan & longer body and longer narrower wings, at least the ones I've seen.