"Are you completing your homework?"
Translation:Sidder du og gør dine lektier færdige?
The addition of ved is one of the three common ways to make a progressive form in Danish. Ved literally means "by" or "at", and it's used in the "at være ved at gøre noget" to mean something like "to be at doing something", which would be "to be in the process of doing something" in more proper English.
It is actually explained here: https://www.duolingo.com/skill/da/Verbs%3A-Gerund/tips-and-notes