Could someone send me code for platforming, like, Mario-style. I need it for a boss fight.

An important thing to remember is that a variable will be needed for Y-speed. Upon jump, set it to a certain negative value (depending on negative jump height.) Every frame, set the player's Y location to its current Y location plus the variable, but also add a certain amount to the variable (depending on gravity speed), until landing.

Could you show me an example?

Try to visualize your character jumping from one side of the screen to the other. In geometry, this path is known as a "parabola."