Imperfective? plrease...

[Katerina James]

In fact, through the Greek colonies which began to appear in southern Russia from the seventh century before Christ and through commercial and cultural contacts in general, the peoples of the southern Russian steppe participated in classical civilization.

En fait, a travers les colonies e Grece quel commencaient a apparaitre en la Russie de Sud le septieme siecle av J.C. et a travers les contacts commercial et culturel en general les gens de la steppe Russie de Sud participaient en la civilisationn classique.

Merci beaucoup!

[Erwan]

En fait, à travers les colonies grecques qui commençaient à apparaître dans le sud de la Russie  depuis le septième siècle av J.C et à travers les contacts commerciaux et culturels en général, les gens/habitants/peuples des steppes du sud de la Russie ont pris part à la (construction/l'élaboration de la )civilisation classique.

[Katerina James]

That was awesome, Erwan..

[Neil Coffey]

In its strictest sense, "peoples" in English would refer to "peuples/populations". Assuming that the original poster really did mean "peoples" in the plural (it's quite rare).