For your optimal saddle height, use the heel method. You sit on the saddle and place your heel on the pedal. This is at the lowest point. The knee should be extended in this position. The distance between the saddle and the handlebars should be such that you can reach the handlebars with your arms slightly bent. The angle of the saddle should be horizontal.
Before training, make sure that you do not develop a hunchback. To do this, move your pelvis slightly forward during training so that your spine takes on the natural S-shape. This prevents possible back pain.