You should prohibit access to the second level from the beginning. So, player can reach it only when he completed the first one.
Add 'Return' buttons on scenes to let player come back to main menu without closing your game.
It would be great to provide more description for your game to let the user understand how to play. It is unclear that you have to avoid small red balls during the first level.
The number of lives is not displayed until you loose one.