my 45 day old gsd puppy acts crazy?

it's totally normal! he's just being a puppy!

buy a dog pen, it will keep him out of mischief, and the pen will help with the biting issue.

when he bites you, say no in a stern voice and leave the dog pen for a few minutes. if you're playning with him out of the dog pen, say no in a stern voice and put him in the dog pen. she'll realize that biting=no more play, you can also put a toy in his mouth when he bites you.

make sure he has lots of toys & always praise him when he's playing with them

dog pen:

http://petus.imageg.net/PETNA_36/pimg/pPETNA-51716...

He still needs the socialization from his siblings and mother so take him back! He thinks you are his litter-mates and wants to play.

get rid of it

Especially with such a young puppy, there needs to be training in order to correct this behavior effectively. I know that this can be very difficult, but I also have a link for advice on ways to manage some of these common problems.

http://provenpetsolutions.com/blog/modifying-your-...

They have some helpful information for dealing with your dog's behavior, which has helped me in the past. Hope this helps!

Its Normal! Haha you were in my situation before! Buy him lots of toys and chew food. I mean a lot. My gsd is now 4 months old he somewhat calms downs but still chews on my pillows and blanket. Dont worry by the time his adult he will start to calm down.