A person who is always looking for prostitute, is called what?
I've never heard a slang word for that. Prostitutes are fairly easy to find in most big cities, so a man would not have to look very hard.
fell shy of = fell short of?
"Shy" is often used to mean "not quite." So to "fall shy" of a goal means that you just barely missed it. The rainfall last month was just shy of a record for September.
Fresh off = ? Why not using gerund = freshing off?
Because it's an adjective, not a verb. Fresh means "just picked" (a fruit), "just laid" (an egg), "just baked" (a loaf of bread), etc. So it's been extended to mean anything that has just been created, found, or renovated. "Fresh off the press"--this morning's newspaper. "Fresh off the boat" (abbreviated F.O.B.)--an immigrant who just arrived and knows nothing about life in our country. So "fresh off... a reveal" means that the product was announced recently and it is just now (today, or this morning, or maybe five minutes ago) available for sale.
Besides, "fresh" is not a verb: the verb is "to freshen."
Ahoy = interj.Nautical Used to hail a ship or person or to attract attention. Is it used correctly here?
Everyone understands the more common terms of nautical slang so we occasionally toss them around for variety. E.g., "loaded to the gunwales (pronounced gunnels)" refers to a ship that carries so much cargo that the gunwales (the openings for the cannon barrels) are just barely above the water line and it might sink in a heavy storm; so to say that about a truck, a shopping basket, etc., means that it is heavily loaded and could easily topple over.
So to use "ahoy" as a greeting would be understood immediately. However, it's uncommon and anyone who says that is probably a sailor (professional or hobbyist), or pretending to be one.
The greyhound is a breed of
sighthound (also called "gazehounds" although I've never encountered that word myself) commonly raised and trained for racing.
Dog racing is a brutal business. When the dogs become too old to win any more races, the owners almost always have them euthanized. There is a huge movement in the USA to stop this practice, and many organizations exist which collect the retired dogs and find new homes for them. Greyhounds actually make extremely good pets (they don't need their own racetrack to exercise on every day

) so this movement has been quite successful.
So to point out that someone has a retired greyhound is to imply that they are very kind and charitable.
Sighthounds were developed in the Middle East thousands of years ago and include the whippet, the Afghan, the saluki, the borzoi (formerely called the Russian wolfhound) and various related breeds. They are so named because they track their prey by sight rather than scent. Most dogs have terrible vision and could not easily do this. By human standards even "keen-eyed" breeds like poodles and retrievers are very close to "legally blind." Lhasa Apsos can barely see at all and might as well carry a white cane (mine trip over their own toys), but they use their excellent hearing more than their sense of smell--the reason they're commonly used as watchdogs.