I do not know how your page looked like before, but The Full-width template should look like this (Stretched header on the top and copyright area on the bottom of the page), with the margins on the content, and of course without the sidebar widgets. Can you explain to me in detail how exactly you want your page to look like?
PS. I see that you have enabled the sidebar position to the left … Please try to change the sidebar position to the right, sometimes that could be a problem. https://prnt.sc/l0x56y