Luis - try to find a professional instructor.
After 5 years of riding you should be able to sit to the trot. My worry is that if you practice on your own, then you might be practising incorrectly in which case you will learn to react incorrectly.
The most important issue for an newcomer is to learn to sit in the saddle correctly. You must sit upright, weight even on both sides, with the legs falling down either side of the horse's belly, with the feet pointing forwards and parallel, toes up, heels down.
The hands must hold the reins in two hands, with a light contact on the bit, elbow to hand to mouth in a straight line. The hands must follow the movement of the horse's neck.
You must use your leg aids in conjunction with your hands.
Find a good book on riding And persist.