"How long was he getting off that streetcar?"
Translation:Jak dlouho vystupoval z té tramvaje?
Then I would say something like "How long did it take him to get off the/that tram". The default sentance sounds to me like he was trapped in some kind of alternate dimension, where he was perpetually getting of a particular tram im a continuous loop before beeing rescued and someone wanted to know for how many eons his torment lasted. I mean yeah, it's gramatically sound but sounds very unnatural.
"Jak dlouze..." in a question can be found in only 2 hits in the Czech national corpus in a single article by an author how claims he has been living in Austria for 30 years. I would avoid it until you get some feel how natives use it. There are more hits for relative clauses, but nothing too many either.
Dlouze is the adverb for dlouhý and is used for both the spatial (bookish) and the temporal tense. However, asking about some duration "Jak dlouze..." sounds really weird to me.
dlouze přísl. k dlouhý
2. časově rozsáhle (op. krátce): podívat se, usmát se d.; vypravovat d. (d. a široce) rozvláčně; vyslovovat samohlásku d. nebo krátce
Take the last one: vyslovovat samohlásku d. nebo krátce To pronounce the vowel long or short. It means prounouce it as a long or short vowel. If it were douho, it would be about how long was he trying or repeating or exercising pronouncing that vowel.