Hn making a smooth fast Gravity Engine with Wall Jumping? No problem, I've got just what you need, all you have to do is remix or see inside. In full, the engine is 128 blocks and to show it's smooth nature, I've used the same one as in The Rainbow Dude (links below).
Make sure to heart and favorite! This is based off of Griffpatchs engine though changed to fit Scratch 3.0. The Rainbow Dude 2: https://scratch.mit.edu/projects/343505226/