Some important information was missing from your message which might enable others to help you: the names of your ancestors and where it is they went from Germany.
You'll be more successful if you post two separate messages, one for each of your great grandparents. Be sure to include as much vital information as you can: first and last names, maiden name, birth dates and places, where they lived, spouses and children's names, birth dates and places.
Remember to work backwards from yourself, one generation at a time.
If you haven't already, take a look at Cyndi's list at http://www.cyndislist.com/jewish.htm
for some very useful links.