Hello.
Can i change the width on Focal theme for the whole site?
Please help 
@Brozko Please share your store url along with password (if any) and describe the issue in more detail.
@Brozko - can you please share your website link? we will need css for it.
You will need to put in below code to the last line of your under your base.css
by going to your store admin > Online Store > Themes > Actions > Edit code > Assets folder.
https://help.shopify.com/en/manual/online-store/themes/theme-structure/extend/edit-theme-code
.container, .shopify-policy__container {max-width:1600px;}
You can play with 1600px to play with the width of your store.