Reference

German grammar

German grammar is mostly one problem wearing several hats. Cases decide the articles, the articles decide the adjective endings, and gender decides the article, so the parts that look like separate topics are the same system seen from different angles. These pages treat them that way.

Which one to use3

A2Elementary

Akkusativ vs DativThe accusative marks the direct object: the thing being acted on.
Wissen vs kennenWissen is for facts and information, and it is what takes a dass, ob or wo clause: ich weiß, dass er kommt.

B1Intermediate

Als vs wennAls marks a single completed event in the past, as in als ich in Berlin wohnte.

Reference1

A2Elementary

German noun gender (der/die/das)Gender is more predictable than it is usually taught to be.