Today I managed to install the new shimano pads.
Their pin was too large and so I had to take the cantilever from my brother's bike.
Now the bikes brakes correctly.
My brother's bike cantilever mounted on mine with new shimano pads
Less configurations available on these cantlever
More cantilever angle
Rear brake
Other details
These cantilevers do not have to move the pad's pin vertically or to set the toe.
However they work pretty well.
One of them has about a degree of unwanted toe, so the pad touches the rim only with one extremity, but with use it will contact correctly.
So the restoration is complete.
Thank you very much.
Lesson learned: never buy cheap unbranded brake pads!!!