Sidebar disappeared

Hi!

I am currently preparing a new version of my website on a local basis before putting it online -I am using a child theme with TwentySixteen etc. but I have a problem with my sidebar.

It is simply not there! I guess it must have smthg to do with my function.php, but not sure as I am a layman here.

I am using Visual Composer, Slider Revolution & Ultimate Social Media Icons as plugins.

Also, these are the only Custom CSS modifications I made:

.site-header{
padding:3px
}

and

.site-main > article {
margin-bottom:5px
}

Thanks for your answer and help!