Who was Obi Wans master

Aah!! OK, technical it was ok, but there wasn't much action.

"Well timed?" Surely you jest. Given the lightsaber duels in E1 versus Obi-Wan's last fight, it really doesn't add up that he should move like a snail on sleeping pills. Why did he let himself get beheaded, anyway?
Was that his "destiny?" 😕 If you destroy me, I will become more powerful than you can imagine...

With the powerfull thing, he meant that he would perish BUT that he could train Luke, who will convert him back to the Light Side.
He let himself be decapitated so Luke and the others had enough time to get away.

Look, the Vader vs. Obi-Wan fight in ANH was a duel of Old Masters, not young athletic swordsman. This sort of thing is perfectly consistent with real life where old men who can barely move are still at least the equal of young, athletic people in a sword fight, even though they cannot hope to move as fast, simply because they are incredibly efficient and know when and where to strike.

HOWEVER, once you factor Obi-Wan's declining skills in the intervening years and Vader's injuries into the equation, the two were NOT as good as they had once been.

Yes, he let himself be beheaded (actually he faded out first) because it was the only worhtwhile option in the circumstances; he had his cool Ghost Trick plan anyway.