Daniele,
Pay no attention to the critics.
It's nice you have made the effort to translate for us. Thanks.
The whole individual-leg thing is not really about strength in the classic sense of the word.
It is about agility as related to balance as related to power output as a function of continuity of positive force through 360 degrees rotation of the crankshaft.
If you will just pay attention to your body you will very likely notice many imbalances which affect the function of it. My main imbalance is an extremely weak left hip; bordering on disability.
The reason for individual leg pedaling is that it forces our leg to work alone and to do the job we ask of it, w/o assistance. This is when we can notice weaknesses most.
Leg presses are not going to improve the ability of my left hip to lift druing the pedal stroke. Lifting with the left hip during the pedal stroke, WILL.
Ironing out teenie tiny imbalances will yield far more improvements than mere increases in strength.