I clearly don't understand something
I don't understand so many things.
I keep seeing, for example, Germans using the words "der" or "die" as "he", "she", or "it", or as "that". I thought the neuter article "das" is used as "that". I am so confused, and stressed out. A lot of the words I thought I knew the meaning of don't make any sense to me when used in sentences!
I am at a point where I only know the nominative and accusative cases, so it could be I will probably learn it, but I am not sure.
Please help me!