I think most of the people here already point out the obvious stuffs that need improvement. One thing i would like to advice is you may want your first level to be the easiest so that players could learn and get used to the controls. Smaller level and less spikes. Once the player progresses you can slowly expand and add more obstacles.
Another thing u may want to consider adding is some sort of a second chance mechanics in the game where if a player touches a spike, give him a 0.5s window to press jump again to save himself. It would make the game more fun and less punishing.
Good attempt here and keep improving! All the best :D