"Banana rolls" under butt

Hey community,

recently I noticed that my booty does not look as good as it used to, probably due to my desk job and growing "older". I am 25 years old, 168cm in height and weigh 55kg. In general I'm happy with how I look since I'm quite slim.

Still I'd like to get rid of those banana rolls under my butt, or at least to tone it. Besides my desk job (where I try to integrate some excercises when nobody's watching), I do have a pretty active lifestyle and own 2 horses that make me move a lot but as it seems it's not enough to stay in shape ;)

Since my timetable is super full, I can only squeeze in 2 workouts a week and some excercises in between at work. What would be the best workouts or excercises to give my butt its former nice shape back?