AR Shoot game

I'm developing an AR game. The goal is shoot the bird down. I'm completely new in c# and Unity3D and I bought a course to help me how to build this project. Now I need to do some modifications to the original version cos I don't want my job exactly the same and I'm struggling a lot to make this changes. I will make a list bellow of the main changes and we can talk better about them. 1- I need to remove the rounds and divide the game in only two levels. (I'm having trouble cos now there is a system of bullets connected to lives and I wanna remove it. 2 - Level 1 the player has to kill 10 birds with 5 bullets only. If the player die or kill the 10 birds the system loads an screen where you can restart the game or quit and your score is showed as well as an animation based in 3 starts that will appear according to the points. (ex: 1-2 player get only one start, 3-6 player get 2 starts...), just an idea... 3 - Level 2 start, I need to put more birds on the game and flying faster to make harder. The player has to kill 10 birds again with 5 bullets but there is also a timer. If the bullets and the timer is over the player lose and load the game over screen but also shows the points based on the starts hank + restart game + restart level + quit and if the player wins I would like to have a nice animation and then comeback to the intro scene. The base for that is done, I need someone to change the Scripts and apply this modifications...