Hi! a very nice game with lots of room for improvement.
I completely agree with the comments about colliders and friction which are very important in this case. Beware of the ground detection also since it failed me to the point to need to restart continuedly.
My best recommendation is to learn how to prioritize your tasks. MoSCoW is a good technic for doing this. And also focus in something before trying to add more and more things. For example, Imo it would be better to have one polish level rather than 5 that have tons of bugs.
Please keep the great work!