My 8 months female GSD developed a new behavior, when I am back to the house after work, she gets so excited,she will run,jump and cry as she is bitting me. she cries alot now and bite ,not hard of course.I am working in correcting her nipping.I never seen her crying out of happiness before.

In my opinion, it sounds like a submissive or anxious behavior. The crying and whining is definitly a submissive anxious reaction to you. Biting may just be a nervous behavior because of the excitement/anxiousness she feels. Correcting it will only make it worse. It could have developed as a reaction to an overly dominant display from you towards her. I had a female, same age, who was exactly like this. Is she typically a "soft"/sensitive dog - you only have to tell her once by just raising your voice, right?

Try not to tower or lean over her or baby talk her when she acts like this. Leaning is a dominant display and will make her whine & the talk in a high voice just excites her more. Instead, calmly pet her and ignore the biting and whining. Kneel down at her level and pet under her neck and chest. If she rolls over on her back, pat your chest and bring her into a sit position. Try to build her confidence and praising her through out the day. She is young and it could be puberty or just a phase she is going through. My dog got better with time and I concentrated on socializing her and letting her feel like the "winner" when we played to help build her confidence. She was much better at a year or so- the whining stopped.
Alison Voore

Now that you mentioned, this just happened after her first heat.yes she is sensitive,when i raise my voice she obey.
I will try to calm her that way.Thanks