"Our horse is eating slowly."
Translation:Nasz koń je wolno.
When should I use wolno and when should I use wolniej? I used wolniej in this sentence, an adverb, because it was related to the veb to eat...
'wolno' is just an adverb, and 'wolniej' is a comparative form of that adverb. It means 'more slowly' (than something).
are powoli and wolno the same? Here both work but I wonder if there are some exceptions
If it means "slowly", then yes.
But "wolno" can also mean that something is allowed.