Hi and welcome
I too am English but currently living in Australia and my passion has always been German Shepherds, though at present I have a Kelpie X and a Blue Heeler.
First, I would take your doggy to a Puppy Pre-School, she may be a little to old for some but there are ones which will take them up to 16 weeks old. Make sure they only use Positive Reinforcement Training, most vets hold puppy classes as this is a safe environment for a youngster. You'll learn heaps, plus your doggy (what is her name by the way) will get to socialize with others around her own age.
Secondly, buy a clicker, they're cheap and the best training tool you'll ever have. If you're not sure how to use one, Kikkopup has an excellent video on starting to use a clicker. Your doggy will need to be 'loaded' with the clicker before you can use it in training. This is quite easy. Just get her facing you, do NOT ask for anything, not even sit, and then click/treat (use high value treats) at least five times in rapid succession. Then when you use the clicker for training, the moment she does what you want - i.e. sit - CLICK/TREAT. At first, with anything new she is learning, reward quickly with the treat after clicking, then as she become more used to the exercise you can leave a longer time between the click and the treat, but the click MUST still be right on the knocker when she does what you want. But DO make sure you click the nano-second she does as you want. Also if you click accidently, and it happens to us all, you MUST still reward. The clicker is the MARKER and if you click and do not reward it will become meaningless to your gal.
A good exercise for you to do is to get some small toy, one which wobbles or moves is great, then get someone to start the toy in motion and you click the second it starts. Sounds a bit weird maybe, but it will sharpen your click rate which is important when using a clicker for training.
I would also find a very good Positive Reinforcement Doggy School and enroll her. DO go down and check the school first before signing or handing over your cash. Any sign of anything other than P+ walk away, believe me it's not worth it to enroll with any other type of school. Personal experience here
Most require the dogs to be three months old and of course be update with their vaccinations.
You haven't said what your gal can do at present. If you would please list what she can do already, like sit etc. it will enable us all to help you with her training. Is she potty trained etc?.
Do please remember PATIENCE AND LOVE, together with lots of praise, are essential elements in training your dog. She may be a fast learner or a slower learner all dogs, even ones from the same breed, learn at a different rate. As such it is important that you TRAIN AT THEIR RATE, not yours
Frustration will set in at times, happens to us all even experienced trainers, and if that happens end the training session on a happy positive note, walk away and take some deep breaths LOL dog training is a wonderful way to learn deep breathing!
Length of time in a training session. This will vary. Some youngsters (and even older dogs) have the concentration span of a Gold Fish, some just want to train and train and train,my Leaf is one who gives you a very surprised look and asks for more if you stop training under 30 minutes, but this is not the normal rule. The average time is around 15 minutes, though at school they'll do a full hour but it will be very varied work depending on the school.
German Shepherds are very intelligent dogs and as you would know a working breed. As such they do require a good walk each day and plenty of physical and mental stimulation. Fail to do this and they'll make their own entertainment, which you'll probably not be exactly over the moon about
But they are also grand couch potatoes, once they're had their walks and play, training sessions, more than happen to snuggle and watch a good movie with you.
As I said earlier, if you could give some specific about your gal, it will be easier for us all to help you with training her. A well trained dog is a sheer joy to own. And above all HAVE FUN enjoy the puppy times, they don't last all that long.
Can't really add much to what's been said. I hope you'll come back and join in the forum. Enjoy your girl, they grow up so quickly! If we can answer any questions or help you with anything, please ask.
View attachment 2799View attachment 2799
GSD's are generally very intelligent and a keen working breed. She looks gorgeous in your pics. 
. I don't know if Ripley was ever hit but I know that she shys away if anyone move a hand towards her too quickly so I suspect she may have been. Breaks my heart.