how do you limit the amount of times you can jump?

Have a counter and check it when the player presses the jump button. If you haven't hit the maximum value, add one and jump. If you have, don't jump. Reset the counter to zero when they can jump again.

You'll probably want to use variables. There's an explanation about these in the YoYo Games WIKI. Check it out when the server is back on.

add a variable in the startevent like:
maxjumptime = 10
then in the colision event with a wall add:
maxjumptime -= 1
ifn the keyboard event of the key u need to press to jump add:
if maxjumptime > 0
{
the code;
}