Translation:The tourists were exiting the train for five or six minutes.
I (native AmE) would interpret your sentence as meaning that they were leaving the train after 5 to 6 minutes had passed, rather than that it took them 5 to 6 minutes to get off the train.
-- EDIT to add an example --
The meaning of the suggested sentence would be more like, "The tourists were leaving the train in 5 to 6 minutes after they got on it" VS "For 5 to 6 minutes the tourists were getting off the train."
Should allow exiting "from" the train. US English often omits words like this, whereas UK English requires them. Another example is where in the US, you protest something, but in UK English you must us protest "for" or "against". It's also marked as transitive/intransitive too. So, as an intransitive verb, you must use "from".
I have added alternatives that include "from," as Oxford Living Dictionaries supports it: https://en.oxforddictionaries.com/definition/exit. Sample sentence similar to the one in this exercise: "‘While I was waiting at the arrivals gate, a large group of people exited from the flight previous to the one I was waiting for.’"