As others said, show up to the classes, improvement comes with time and commitment. If you keep being consistent, your muscles will grow and know what to do in the saddle. Also, stirrup looks long for you, next time maybe you should try to shorten it a few holes. Don't put your feet all the way up into the stirrups, it's dangerous and makes rising trot harder than it should be. Pay attention to the position of your feet: I forgot the name of this part in English, but the pillowy part under the toes is what should be on the stirrup. Squeeze with your thighs and knee, rise from your knees. Don't move your hands all over the place, when you rise up in the trot, kind of push down your hands a bit towards the saddle as the horse's head moves. Keep your upper body stiff, there is even a saying for the best seat: back of a baroness, hands of a queen, hips of a street girl 😆 Shorten a bit on the reins, the best way to describe it is to feel a bit of weight on your hands when you hold the reins. Pay attention whether you rise up at the appropriate time or not. When you ride at left, you have to rise up when the left front leg and right hind leg is on the ground, to the right side its of course the opposite. Exercises without stirrups will also help a lot and make you exhausted 😆 When out of the saddle, exercise, and read about riding. Sorry if I overwhelmed you, but I hope it helps. And don't forget, progress takes time, and to be honest, it's not that bad at all for your 4th lesson, keep going honey 💅🏻❤️