Theme Tesseract | Right Alignment of all pages, like there was a sidebar

Hello. My name is Amanda. I am a brazilian guitarrist and my site is: https://www.comoaprenderviolao.com.
I use Tesseract Theme.
After some little changes on Style.css (moved to Child_Theme) to change some buttons’ color (buttons that are not those which I can change with the code given by Tyler), in contact form, per example, something went wrong with my website. How you can see, footer and header are good, but all other content (and in all pages) the position is more to right, like there was a left sidebar.
I’ve tried to upload the old style.css to Child_Theme, but nothing changed, except buttons’ color. If I am not wrong, there was in the page editor a box that permits me to chose between full widht template or default template. But now it is gone.
I can not say that this problem have the root on those simple changes in the color’s html code, because others changes was made using WordPress. But those changes was so innocents, like including images, texts, et cetera, that I can not imagine that this could possibly be the reason. Perhaps, they are not so innocents… I do not know.

I really hope you can help me. Maybe this is a problem with an easy solution, but, because I am new at theses thing, I need some help.

Thank you all in advance!