How to Improve score for PageSpeed Insights?

Hi all,
My website is https://mumtip.com
I use WordPress for my website.
When i check PageSpeed Insights from Google the score for Desktop is around 85 and for Mobile is around 71.
Link here : https://developers.google.com/speed/pagespeed/insights/?url=https%3A%2F%2Fmumtip.com%2F&tab=desktop
I want to improve the score for my website.
There are some problems that PageSpeed Insights show:
1/ Eliminate render-blocking JavaScript and CSS in above-the-fold content
2/Reduce server response time
3/Leverage browser caching
4/Optimize images

I try to install many plugins to fix problems above but no improvement at all.
I also try to contact Hosting Provider but not much help from them.
Can you help me solve the problem?
I would really appreciate any help!

Thanks