I'm surprised that a pup is away from its mother at five weeks old? My understanding is that seven to eight weeks is normal.

The breeder must have weaned your pup onto some sort of food? You need to find out what this is (if you don't already know) and feed your pup four times a day, at least, at that age.

As for training, the only thing I'd consider at that young age is getting a pup used to a recall, ie coming back to their name.