May I suggest you go to a solicitor or accountant, who really know the law on letting (unlike MOST including real estate agents) and get all the info on what you need to do in order to legally let, and to ensure that you do give the tenant a longer period of right to stay, than you may intend. Those who rent often have more rights than the owner.
If you have a contract in Spanish ( in English is almost certainly not enforceable) unless it is duly registered, I believe it unenforceable, if registered, and you have not complied with (all) the other requirements, you may have problems anyway.
Legally letting a property is not straightforward. My son has left his apartment empty, that was far easier.
Good Luck.