So the preposition "о" takes the prepositional case as a rule instead of the genitive?
Yes. It is primarily used with Prepositional. There is only one use of о/об with Accusative, the one of coming into physical contact (by hitting, rubbing, leaning, stumbling, getting your clothes caught on something sticking out):
- Я споткнулся об камень. = I stumbled upon a stone.
- Я поранил руку, ударившись о стенку контейнера. = I wounded my arm, having bumped into a wall of the container. (partiticples, physical contact, verbs we do not have in the course —pretty advanced stuff here :))
Спасибо болшое! I already speak a slavic language(serbo-croatian) and the grammar is in many ways similiar. But the language is still so grippingly fascinating. Thank you for this course.