The art is great, but that platforming needs some woooork. Not bad for your second game ever though!
Try these fixes:
For your character, check out this character controller to fix your velocity issues:
https://github.com/Brackeys/2D-Character-Controller
And to fix the wall sticking, add a slippery physics material to your characters RigidBody2D:
https://docs.unity3d.com/Manual/class-PhysicMaterial.html