I can't translate it, but a streak means continuous success at trying to accomplish something. In the case of Snapchat, it means that two people have sent Snapchats to each other for that many days. So, a Snap Streak of 10 days means that those people have sent Snaps to each other for the last 10 days.

I think the meaning you're looking for is 'consecutive/in-a-row'. For example, a snapchat streak usually follows a number. If it says 5 then you've had 5 straight/consecutive days of "snap chatting"

Oh, thanks a lot!