Replacing theme ruins website

Actualy you are using Twenty Eleven on that URL. So, no body can see what you are talking about ??

By the way i see this error on inspector:

Failed to load resource: the server responded with a status of 404 (Not Found) https://www.agamy.co.il/wp-content/themes/twentyeleven/sidebar_style.css

There′s no sidebar_style.css on that folder.

I cant show you because I cant leave the broken theme on. but here’s a screen shot of how it looks like.
https://www.agamy.co.il/?p=5675
there wasnt any sidebar style…I use twenty eleven custom child theme.

and here how it suppose to look: https://brandon.agamy.co.il/
Ive installed a subdomain

I’m sorry but as you appear to be using a commercial theme, you need to seek support from the theme’s developer/vendor. We do not support commercial products here.

Ive tried their support =\ but they say the problem is in my wordpress.
Also I tried to install some other themes and the problem repeats – the nav is all messed up and the sidebar is somewhere down