'This game made me very angry but didn't do much' about sums it up! Anyway, I did play it a while ago, so it may have been updated. Here is some gameplay anyway - 15:07 to 18:27
If you hold a direction and dash you will dash in that direction, so you can dash upwards and also diagonally. For the first jump you struggled on you should jump and dash diagonally up-left, and after that just dash upwards.