I am an Australian citizen, my grandparents and mother were born in Germany. They migrated to Australia when my mother was 8, does this make me eligible for a German passport or any other entitlements?

There are many facts that you leave out here such as citizenship of family members when they migrated. What nationality is your mother now? Etc.

German citizens can maintain dual citizenship only in case they were born overseas or one of the parents are foreigner. Besides, you have to live in Germany for a period. For further info, contact the nearest consulate.

My mother is an Australian citizen now as well as my grandparents. When they migrated they we all German Citizens.