Translation:Wij verzamelen alles!
I don't think this translation is correct. 'We are collecting everything' should be 'Wij zijn alles aan het verzamelen'. 'Wij verzamelen alles' should be 'We collect everything'.
I think both Wij verzamelen alles! and Wij zijn alles aan het verzamelen! are valid translations. In Dutch simple present (e.g. Wij verzamelen alles) is often used for things that are currently happening. E.g. a context could be that some people are gathering some things that are spread around in a room.
There is a difference in English between "We collect everything." and "We are collecting everything." Is there no such difference in Dutch? I translated this as "wij zijn verzamelen alles"
What lessson should I have learned verzamelen in?? Because I cannot remember ever learning it.
"Alles" is "everthing" in general. "Alle" you would use like "alle mensen" (all people), "alle vrienden" (all friends), and "al" you would use like "al zijn vrienden" (all of his friends), or in sentences like "ben je er al?" (Are you there already?) These are just a few examples of when I would use them, but here is some better explanation: http://www.dutchgrammar.com/en/?n=Pronouns.Id04