Sorry for the delay in answering.
At first, I would suggest you to reduce server response time http://prntscr.com/e1178b because this is one of the most important things if you want to make your site faster.
Also, you may try query strings remover plugin https://wordpress.org/plugins/query-strings-remover/ to fix some GTMetrix notices.
Make sure that you minified CSS because you still have “Make fewer HTTP requests” notice.
There are many tools to help you with minification during development. You can also use a plugin, such as WP Rocket.