just use the normal arrow keys or WASD There is currently a bug for the try-again feature so i would recommend using the green flag. The try again button pops up if you press the green flag twice and touch the spikes, but before you click try again make sure to hit the red stop button. That makes it less glitchy.
https://scratch.mit.edu/projects/764029151/ helped me a lot. i watched the guys tutorials so huge credits to that dude. This game is very similar to the other game, but i will add extra things to it so that mine is more original. ScratchCatThings helped a lot. sub to him