Dont worry about speed, that will come with time, you want to focus on clarity and cleaniness. There's no point on playing the arpeggio sections (or anything for that matter) at ungodly speeds that cant be handled yet and making them sound like you've just stepped on an exploding anthill. It might not seem so in the process, but the piece is learned MUCH faster working systematically and slowly. Take the arp section at a speed that is clean and flawless (even if its 40bpm) and then only when you're absolutely sure it is perfect many many times in a row, speed it up just a LITTLE. (like 2 metronome clicks) and work your way up to speed like this.