"You are biking a route."
Translation:Jij bent een route aan het fietsen.
What is the rule for "aan het" - once the order changes (Ik ben een route aan het fietsen) and another time not (Ik ben aan het betalen voor het gemeenschap)?
Usually "aan het" + verb come at the end of the sentence. However, if you have a prepositional phrase (like "voor de gemeenschap") it can also come after.
"Ik ben voor de gemeenschap aan het betalen" is also correct, and even a slightly more common word order.
What does this mean exactly? That you're driving your bike through a specific route (as in road, i.e. location) or going from one place to another (route as a path between points A, B and C)?
The sentence simply means that "you are cycling on a route", so it can mean both descriptions that you gave, Luis.
I was trying to conjugate "fiet" and got "fietst" for "je" but answer is "fietsen" as if multiple people. I assume the rule applies to all "tst" verbs?
The stem of the verb fietsen is fiets, so it is just standard conjugation with a t added for 2nd and 3rd person singular (je fietst, zij/hij/het fietst).
However the conjugated verb in the sentence is bent. The continuous in Dutch is formed as follow: zijn + aan het + infinitive. So the infinitive for fietsen is used here.