how many times in week should i groom/ brush my 38 day old gsd pup?

Combing or brushing your dog's coat should be done 2 to 3 times a week when your dog isn't shedding. During shedding season, you will want to comb or brush your dog daily. Right now, the main purpose of combing/brushing your dog is mostly to get him used to the process. When you groom him, be sure to touch him all over his body. Also make sure you handle his feet 2 to 3 times a week. This will accustom him to having his feet handled and make it easier for you when you need to clip his claws. Also open his mouth and look at his teeth, just to get him used to the process of having his mouth handled. This early accustoming him to being handled, inspected, and groomed will make things much easier for you, the vet, or anybody else who has to handle him. If he throws a temper tantrum, gently but firmly restrain him, continue handling him, and be sure to praise him when he cooperates with you.

Grooming as in bathing, About 2-3 times a year.

Brushing2-3 times a week to remove loose dirt and fur.

yes, u should do it at least once a day if ur dog is furry. If its not then at least four times a week.