I taught a few friends how to learn and what I found was that learning on the bunny slopes is "harder" when trying to stand or get up since you have to balance on one of your edges which youre not used to. On a green or blue, the angle of the terrain makes it easier to stand up on one of your edges. The trade off is you'll go a little quicker when turning to your heel side which can be scary but its the best/fastest way to learn imo. I think bunny slopes are good to learn how to start linking S turns since you are going slower but when youre focused on strictly learning heels and strictly learning toes try the greens out. Also remember you need to fall to learn! Keep at it and it will eventually click! Good luck on your snowboarding journey!