Your printscreen says that the total payload of the website is 750kb. With 3g speeds of ~350 kb/s (slowest according to https://en.wikipedia.org/wiki/3G) this shouldn't take more than ~2 seconds to load.
Looking at the print-screen it also seems like the fonts take quite a bit of time to load.
Since it takes 9 seconds I'd look into using a CDN for faster loading (CloudFlare, Fastly and CloudFront are popular), I think that may help quite a bit.
Second step may be to get http/2 (e.g. via CloudFlare) for multiplexing (faster downloading of multiple files).
I don't think the size of vendor.js is the main issue here.