K-9 (1989)

The extravagant cop Michael Dooley needs some help to fight a drug dealer who has tried to kill him. A "friend" gives him a drug-sniffing dog named Jerry Lee. With his help, Dooley sets out to put his enemy behind bars, but Jerry Lee has a personality of his own and works only when he wants to. On the other hand, the dog is quite good at destroying Dooley's car, house, sex-life, etc.—Flavio Rizzardi