"Sometimes I sleep in the morning."
Translation:Sommetider sover jeg om morgenen.
i morgen in Danish means tomorrow. So, maybe that is why. But this is just my guess. You probably meant "i morgenen". I wrote the same and did not get it right either.
There seem to be a lot of rules about the usage of prepositions in Danish- for example when to use paa in stead of i or om is a little too fuzzy for a learner, IMHO.
If someone reading this post has a link to some resource that explains the usage of i, paa or om in different conditions, please reply.
Think of formiddagen as "almost noon" or "almost midday". i.e. before midday. It's that time of day that's right after morning but right before noon. Even though in the US, we just call it all "morning", in many parts of the world, forenoon (and thus, formiddag) is more of a thing