i read somewhere that while backing up your truck pushing brakes help self-adjust rear drum brake.
There was a time this was true, I cannot say if it applies to your model. I was once instructed to stab the brakes firmly while reversing about 5mph. If the pedal height doesn't return after a few stabs, the adjuster may be seized. They get washed down with every rain, so they do tend to rust up. in that case the wheels/drums have to come off.
How many click needs turn because tires will be ground.
You really need to adjust them with the wheels off the ground. If the adjuster is seized, it needs to be freed up first. Adjust them as to extend the adjuster out between the bottom of the shoes forcing the shoes until the drum just barely drags. If you adjust it on the ground, you are going in blind and may be over adjusting causing unnecessary drag/wear.
I feel my brake Padel is feel soft and it's going further down then before.
A soft pedal is not the same as a pedal that has lost height from an out-of-adjustment rear drums/shoes. If the shoes need adjustment, yes the point of stepping on the pedal to it actually braking does increase, but the pedal should still be firm once the pads/shoes are making contact. If it is soft you either have air trapped in the system or a rubber caliper line is swelling and about to fail. I would inspect the entire system and bleed all 4 corners before I even bothered trying to adjust the rear shoes. You may also consider getting some test strips to check the fluid for water or high copper levels....
