coding problem

[InfinitePegasus]

Hello, guys; I have a problem with my buttons on my product page. On my product page, I have two buttons; one of them is written Add to cart, and another one is written: buy it now. So I want to remove the Add to cart button and change the Buy it now button to the buy, and I want the buy it now button to shake, you know, like shake when someone opens my product list. I know I need to go to theme.scss.liquid, but I don't understand why the debut theme doesn't have the part or section. So I tried to solve my issues in theme.css, but the problem is that when I went to theme.css, and I searched for Addtocart, there wasn't any add-to-cart code, and that is funny, and I don't know why. So could you please help me with all the questions that I ask? It can help me, and I appreciate your time and your effort in solving these questions. And I do not think that I am the first person who has this problem.