Premium Plugin

I just checked my website on google pagespeed insights and I got the following results:

Mobile: 26
Desktop: 83

Firstly, I want to know if the Fastest cache plugin (premium version) can solve my current issues before I make a purchase.

Secondly, I want to know why the scores are different.

Thirdly, I’m not a developer so I don’t know most of the terms used, so would it be possible to send my website details to you to fix issues for me if after I pay for the premium version and my site doesn’t work?

P.S. I already have the free version installed.

Thanks.

The page I need help with: [log in to see the link]