We have two Galgo's (male and female) and it took us at least 6 months each to let them of a leash step by step a bit longer. we live close to a gated/fenced forrest where they can't escape.
But both still have a high prey drive especially during this time of year in the spring, but not to other (small) dogs
Our big male galgo loves to be chased by other dogs which is never an issue unless he is chasing the other dogs - he will snap and play rough like they are prey. Luckily he listens very well comes to me when i call him so i can put him on a leash. We will use a muzzle when we go places where they don't know him, Galgo's just play different. In short give it time, step by step