Ok, a great progress achieved even that I am not comfortable working with electronics...
After few days of trial and error (measuring, cleaning, soldering on both doors lock assemblies), everything works on my 2001 Boxster alarm, including the alarm button on the dash and turnig of keys on the drivers door for longer time windows going up or down AND NO MORE very annoying double beeps when opening the doors :dance:
Only one minor issue is to still figure out. Passenger door (right side) window does not stay up as the door is open. The window dips when the inner or outer hand lever is lifted, but window goes down again as the hand lever is released. Still a major improvent to the situation going on thru out this spring time.
Would any of you happen to know which microswitch in the passenger door tells the window to stay open when the door is open? I'd prefer to figure out to swap the microswitch or the lock assemby, if I'm certain whis is the correct microswitch for this currently still not functioning smaller issue.