Other people mentioned my confused explanations and this high difficulty at the beginning.
The easiest way to catch the ball in this level it's to go on the right of the enemy (on the right of the screen) and shoot toward your spawn. After, you wait for your ghost to shoot. You just have to right-click at the good timing when you are near the ball (the ball is very fast it's not easy) to catch it.
Thank you very much for your feedback !
I hope if you try again you will enjoy better because it's the most interesting part.