"We will learn Ukrainian."
Translation:Ми будемо вчити українську.
будемо навчатися and навчатимемося has more of a meaning of studying at a school or studying a skill, not studying a subject. You can use the other ones but you have to pay attention to how you use "Ukrainian" with those since the cases will be different, for instance, "будемо вчити українську мову" and "вчитимемося українській мові". However, the latter isn't used much if any.