@CalamityCallout
And here I was thinking it was a good addition, because he literally isn't his future self but a past incarnation with future memories. But having the brain of a child, why would he immediately follow the desires of an old man version of himself from the future? He wouldn't, would he?
@Alex-dono-sama
He probably wanted to get the red magic over and done with quickly because it is what he was already most familiar with, then he could dedicate the rest of his time to the other elements.
@dskilly
Not sure he had a plan. He seems to be winging it. And I've no idea how he knew a spell to reverse time, but from his own reactions to it I'm guessing it wasn't a sure thing. He is almost certainly winging it.
As to why he is joining the girl, THAT much is obvious: Because if he just follows the same route he took the first time through life, he will arrive at the same destination. But he is looking to change his own fate, so on a rudimentary level it makes sense to do significant things differently. Difference is the intent there, though how exactly it relates to his goals, we don't know.
Plus I'm not sure he is necessarily struggling to learn anything so far, but simply getting bothered by the fact that he was doing the same thing as before all over again.