The gate might be toast to my eyes.
As a minimum unscrew it,
set flat in driveway,
wood bleach/cleaner it and let soak in,
power wash, let dry a week or two,
unscrew, bar clamp it back to square, You can 'handshake' these to any length
screw back together with new hardware (stuff rotten holes with toothpicks),
soak with good stain ~ cherry colored two coats would be a guess but always err on the light side
add corner brackets
https://www.strongtie.com/solutions Simpson now makes nice thick black pieces