The Germani were the people inhabiting the lands known by the Romans and Greeks as "Germania" which is current day Germany
The Germani were not a empire like the Romans or Greeks, instead being a vast number of tribes spread across the land. Each tribe regularly commited raids on eachother. Some where civilized, even to the point of the Romans, while others were barbaric, assaulting and pillaging all they could see.
There was no set defined culture for the Germani, due to each tribe differing at least slightly. Some could be religious fanatics, military masterminds, cunning deceivers, or petty warlords.
Their exact language is unknown, albeit their tribal and personal names are mainly Celtic, Possibly due to their lands also being occupied by celtic tribes.