Thanks for playing! Holding the run button lets you build up momentum while moving and releasing it reduces that momentum, even in midair. The idea is that you can use that quick reduction in momentum to slow down so you won't go over the platforms or slide into lasers. What I recommend for the second button is running towards the checkpoint, jumping once you touch it, jumping from the first platform from the side of the blue button once you land upon it and then doing two jumps in which you let go of the run button partway through the jump and then hold it again once on the ground to build up momentum for the next jump. The final two jumps after that can be done without holding the button.