Too many CSS and Javascript files?

Hi,
I’m using No8 theme, I have had my website speed tested(lumirastudio.com tested on https://www.woorank.com/en/www/lumirastudio.com), it seems like that it’s quite slow at the moment, one major issue is that my website has too many CSS(4) and javascript(7) files, do you have any suggestions with regard to improve this?
What are the cuases for having too many CSS and javascript files? Is it because of the plugins I’ve installed?

Many thanks for your help in advance, looking forward to hearing from you.
Regards,
Luke