Site error?

I have a site, I got the white screen of death (I don’t know why I didn’t make any changes). I messed around with plugins and the white screen was gone, but now all I am left with is my top menu bar all over the page and everything else is gone.
Ive tried renaming plugins, deactivating and reactivating and nothing is working. I am getting this error is this possibly it and does anyone know how to fix it??
Fatal error: Call to undefined function twentyfourteen_has_featured_posts() in /home/s2u33/public_html/website name here/wp-content/themes/twentyfourteen/page-templates/full-width.php on line 15

Im a bit of an amateur, I only thought myself wordpress, so if anyone can help a dummie