hi there just looking for some advice.  have a 4 month old gsd and he is barking at people in the street when out walking especially children just wondering is it best to correct him for it or is that normal behaviour for a pup thanks

I would stop him you certainly dont want him to be barking at people particulary children when he is older Perhaps when approaching people you could practice getting him to "watch" you and give him a titbit so he begins to associate people with something good. maybe choose somewhere to stand where there are people and practice for a while

Chances are he's doing it because he's insecure with strangers. Don't try to tell him off as that will make it worse. Instead work with him, rewarding when he's quiet. See a person at a distance and BEFORE he has started barking, praise and give a food reward. It does take a bit of work but means he will learn spotting strangers means something NICE happens.