I have never had that breed, but I have a Pomeranian papillon mix who is a rescue. He will occasionally lunge at one of our cats but not the other. It seems to be food driven, based on the possibility that human near him has food. We worked with treats, one for cat, one for dog as they sat near each other. It helped, but of course, that is the cat who is not food driven.
Petey, the dog is extremely food driven, and also prefers to "hear" the word come only if food is involved. Sadly, I am not consistent enough in the training of him. He had cancer treatment last year and is on borrowed time, so we are more focused on fun than training. Focus on the areas of training that are important, and enjoy him.