I need help with the sneakers. I only get 50 steps but i see the top runs have 90 steps. How do you upgrade them? Do you just need to craft it with more tennis balls? Or do you need 100% completeion?

Oh, so that's what the store is for... Okay

If you want a good time in 100% I would recommend not using the upgrade, it allows for some glitches with the extra stored items to skip some chapters

Another question, is there a glitch to increase the base movement speed without the sneakers?

Not that I know of, I guess you could warp around with the mask but that’s not very helpful in any category