Navigation systems lead a way that is closer but barely manageable by normal cars. I strongly recommend taking the following route:
From Malaga airport drive about 50 minutes in the direction of Almeria and take exit number 274 "Vélez-Málaga / Caleta de Vélez"
Hold left and take a left turn onto Camino de Torrox and continue on this narrow street
On the next three roundabouts take always the first exit direction "Arenas"
Continue until you turn right into the MA-4111 towards "Arenas"
Just a couple meters further you will see the beginning of the gravel road on the left side direction "Fortaleza"
Turn on your navigation system and follow its directions
Take the train from Málaga Airport to the "Maria Zambrano" train station in Málaga. Right next to the train station there is the bus station where you can catch a bus with the local bus company ALSA to Vélez-Málaga bus terminal for around 3€.
From Vélez-Málaga there are NO buses available to get to the Finca.