Volgaen er Ruslands vigtigste flod.

The river is called the Volga in English, but as far as I can tell, it's simply called Volga in Danish.

Volgaen løber fra Tver til det Kaspiske Hav.

Floden stadigt bruges ibruges stadig til godstransport og landbrug.

There's no need for inversion of verb and adverb in this sentence.