Fixed bottom button, weird position - Css custom code

Hi guys fine? I really don’t know much about custum codes. I’m trying some codes that i found here to get a fixed buttom to the bottom of one of my pages, and them he scrolls to the page. I’ve made some changes on him just to center the buttom and its working fine on my desktop. But doesn’t appear on the mobile version. Using the properties of the page from chrome using the mobile view i could see the button he is to the right of the page. On the phone, when i flip him i can see just a little bit of the buttom, but he is there. There’s a way to center that button on all type of views? Will let the codes above, 1 is the CSS of the buttom code, then jQuery one (used on that i found here), then 1 print from desktop and one for the mobile view. Put all in one image cause my limitation to create my first topi. And sorry about my english, Brazilian here.

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