Does anyone have a psych service dog? If so how many commands were they able to learn? What is the most helpful command?

I'm asking because I got a golden retriever puppy to be my service dog. I need her for mobilility and Sza issues and I'm trying to figure out how many commands they can be trained for or if I'm loading to much on one dog and should split the work between 2 dogs. So what is your dog trained for?