Why couldn't be "When does our trip begi"
Assuming you actually wrote "begin", that should be correct too.
I thought Reise wa the plural for Reis
When begins our trip
That's not correct English.
(It sounds like something a German person learning English would say, though.)
Why not "When does our vacation start?"?
Why was the singular "beginnt" used instead of the plural "beginnen"?
What is difference between die Fahrt and die Reise?