Translation:When does our trip start?
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"?