Dog potty training problem need help?

I have a five month old german shepherd and everything i try she wont learn how to urinate and poo outside.after she eats i give her a walk 40 minutes later(25 minute walk) she doesnt do anything just sniffs. i let her go back inside she goes straight to the spot where she usually goes to the bathroom. when i put her in the crate she goes there. can anyone help me