“looking after a friend's dog”
Look after someone or something means to care for them. Tina is temporarily caring for a friend's dog while the friend is away.
A2-47 / CEFR A2 / EPISODE 47
Explaining an animal's condition
SceneAt a veterinary clinic. Tina brings a friend's dog she is looking after; Frank accompanies her.

WORDS & CONTEXT
Look after someone or something means to care for them. Tina is temporarily caring for a friend's dog while the friend is away.
Seem means to appear to be, and may be ...ing means might be doing something. After examining the dog and asking what it has eaten, the vet gives her assessment of this dog. The line does not claim the dog is healthy just because it has been eating human food.
Trick someone means to fool someone, and a treat here is a snack for a dog. The first you is addressed to the dog, not the vet. Right after realizing the dog was waiting for food, Tina sees its sad face and wants to give it one more.
Train means to teach behavior. Normally people train dogs, but here Tina responds to the dog's sad face by handing over more food, so Frank teases that the dog is the one changing Tina's behavior: "I think you're the one being trained."