at the time "proto-Germanic" is claimed to have been spoken, most of Germany spoke a slavic/celtic/local dialects unrelated to what was being spoken in Norway or Sweden and the association was constructed by german nordicists of the 18th century that drove popular indo-european philology based around grammar protocols established by international trade or diplomacy instead of words and tones used by natives in life and labor
At the time of proto-germanic, it would have been spoken only in the northern parts of present day Germany, besides southern Scandinavia. The language spread and diverged during the first millennium AD.
