idk how to make sprites, should he be 16x18? anyone wanna help redesign him?
Size of the sprite doesn't really matter, as long as it's to scale with everything else. A typical pixel platformer would have a screen size of about 256x224 or 320x240, so pick a size that works well within that. Super Mario Bros. is a good model game to study, and Mario in that is 16x16 pixels, or 16x32 when big. Sonic is a little bit larger yet.
If you want guidance on pixel art, I suggest checking out this Discord server:
https://discord.gg/JHhPbyK