"Toget kommer forbi mit hus om natten."
Translation:The train comes past my house in the night.
I would say "goes by my house" - never "comes by my house" unless it's stopping and coming in for a little snack.
In English, "the train comes by my house at night" would have the same meaning as "comes past my house . . ." so that should be counted as correct.
No, "at night" is a common expression in English, and a good translation of om natten -- while "at the night" is wrong.