Is it legal to put a clause in the contract that it ends automatically after 3 years?

Hello, I am in need of some advice concerning my rental agreement. In the
contract, under "Duration" it says, that this rental agreement will end
automatically after 3 years (so this year in a couple of month). So my
questions: Is this legal, can the contract just end like this without no
further notice from the landlord? If so, does he have to ask us first if we
want to renew the agreement before putting it out for new potential renters?
Do we have to accept an increase in rent? And can the landlord increase the
rent as much as he wants? Thank you so much for a short advice. Bettina
Klapp

This it what it says in the contract: El contrato de arrendamiento tendrÃ¡
una duraciÃ³n de UN AÃ‘O, siendo de cumplimiento obligatorio. ComenzarÃ¡ a
surtir efectos a partir del dÃ*a 1 de agosto de 2017, fecha en la que el
arrendador harÃ¡ entrega de las llaves de la vivienda al arrendatario. El
arriendo podrÃ¡ prorrogarse, a solicitud del arrendatario, por periodos
anuales sucesivos hasta alcanzar la tercera anualidad con arreglo a la
legislaciÃ³n vigente, quedando extinguido definitivamente, sin necesidad de
comunicaciÃ³n o requerimiento alguno, el dÃ*a 1 de agosto 2020.