Wait how did you get through that small opening with the spikes on the bottom? I couldn't find a way because of their unfair hitbox and had to moon jump off the wall repeatedly to go over the wall. He should also probably change the default GDevelop platformer game example graphics if he wants to further develop this game into a more finished product too.
Viewing post in UnJump-For Big Jam jam comments
I got through the opening by testing and tweaking the gravity and jump power. I went a bit higher on the gravity and lower on the jump (I think it was in the 150-250ish) range. I didn't recognize that the graphics were default--I don't have much experience with GDevelop. I do agree with you that adding their own graphics would be a great step in polishing the game; the assets don't have to be perfectly crafted but doing their own art or partnering with an artist is very important for making finished product--especially on future projects!