Hey I just now played your game. I like how much work you've put into it and also managed to provide detailed instructions in the game as well. I like it.
However, I guess you are new to game development and I think It would be nice if I give you some feedback.
1. I noticed that the health bar isn't fixed, and the reason behind this is because you have put it in the base layer.
To fix it, simply open the game scene and open the layer panel from top right corner of GDevelop. Create a new layer and name it "UI" (It can be anything). Then move this layer to the top of the list because you want it to always appear on the top. Now from the property of the Health bar, change it's layer from "base" to "UI".
Done! Now it won't move along with the world, It will stay fixed. (Also, I noticed that you've used "Stay on screen" extension to keep it visible, now you can remove it. You don't need it now)
2. You game doesn't have a "Game Over" screen. You can achieve it by setting the condition: When health bar value = minimum value -> change scene to "Game Over"
3. During the dessert, road and grass scene I noticed that it is easy to get out of the grass area which reveals the rest of the unmade area. There is a simple fix to it. Right click on the asset (desert, road or grass) and add "anchor" behaviour to it and then set the "top edge" to window top, "right edge" to window right, and same for the left and bottom. This way the asset will stay stretched on the screen.
4. You can also add something called "Collision box", it acts as an invisible barrier through which the player can't pass. To set it up just make a tiled sprite and name it "collision" and wherever you want to restrict the player movement, place it there(as if there is a wall). Now in the events, add a condition: If player in collision with Collision box -> separate "player" and "Collision", only player will move. (Don't forget to set the collision to hide at the beginning of the scene)
I hope this helps you and your game becomes a very great game.
I spent a lot of time to play your game and write this feedback. It would be really nice if you could play my game (and it would be awesome if you rate it if you find my game interesting)