Looks like a template from templatemo.com that uses bootstrap base (3.1.1) with a vendor file for responsive additions.
Some reasons this is a questionable approach
- Style rule conflicts
- Separates from Bootstrap Grid system (may have unwanted results)
- Bootstrap (last time I looked) has SaSS and LESS files for these kinds of mods
- Huge banner (makes site wider than it needs to be for low-res) Why not use col-sm-12 and use image as BG, or in container element with overflow: hidden?
- Inline styles
- meddley of other third-party scripts and addon’s not meant for “mobile” experience…
N.b.: Honestly I would start again and do less, try to add more further down the line.