"Wij hebben een lange tijd gewacht, maar hij is niet gekomen."
Translation:We have waited a long time, but he has not come.
It's more natural to say 'we have been waiting for a long time but he hasn't come.' using the present perfect progressive tense... to me anyway.
Can anybody explains to me why "hij is niet gekomen" but not "hij heeft niet gekomen"? Thanks!
Why is the present tense not correct? "We have waited for a long time, but he is not coming"
The Duo translation best preserves the tense of the Dutch sentence.
Some Dutch auxiliary verbs support a change in tense when used with an infinitive or with the past participle. For example, gaan+infinitive changes from present tense to future tense. Here, zijn+past participle changes the second phrase from present to a past tense (unfortunately termed the present perfect).