"He came yesterday."
Translation:Er kam gestern an.
Why ankommen but not kommen? Duo won't accept "Er kam gestern" unless I add "an" at the end. But I thought ankommen was more "to arrive*, whereas here I have to translate " he came yesterday".
I agree with the confusion. "Arrived" and "came" are two different concepts and can only be used to mean the same thing with context.
Yes, you're quite right. He arrived yesterday. would be "Er kam gestern an." - he came yesterday = Er kam gestern. That seems to be one of many translation problems done in duo.