There are no smoke and mirrors in this game (contrary to what a lot of SEO agencies try to suggest). If it takes 10 seconds for a page to load, your target audience is going to leave, and so is Google. It has to be developed for all types of devices – If I come to your website and it looks crap on a mobile, I’m not going to think very highly of your business, neither is Google. When you think of the logicality of this, it all makes sense – you build it for your target audience and Google will follow suit. So, now with so much web traffic being mobile, Google’s gone with a mobile first policy – he’s actually going to rank your pages based on its mobile design and layout first and then desktop.