How long does this takes?
Couple of days, a week maybe, depending on travel distanceSo basically nothing here suggests that months need to pass, yet alone a year or more.
Yoda right before Luke fights Vader: Luke! You must complete the training[…]Only a fully trained Jedi Knight with the Force as his ally will conquer Vader and his Emperor.
Yoda a few days later, after Luke gets his ass handed to him by Vader: No more training do you require. Already know you that which you need[…]One thing remains. Vader. You must…confront…Vader.
Sorry dude, but that makes no sense. Either Luke spent some time training on his own while he was busy working with the rebellion, making plans to free Han, and coping with the world-shattering revelation that his dad is Space Hitler…or Yoda has a bad case of Alzheimer’s.