Solid effort making a 3D game with voiceover, a good deal of work! Only issue was the jump mechanic, a lot of the time Id hit space and he wouldnt jump, which made platforming a bit difficult. I cant really talk though, since my entry has similar issues! Going by the feel of it Id guess youre using collisions for ground detection. Id recommend trying out casting a ray downwards, or as Ive just fixed with mine - casting a ray downwards from the front of the player and the back. That way even if youre on the edge of a platform its still 'grounded' because the rear ray is detecting ground. + have a very short timer that allows for a jump even in mid-air after coming off a platform.
Either way tho, nice effort!