Hi there,
the Theme itself is the most optimized there is. The issue is to do with what you have added to the site. Here is GTMetrix report of your site which provides much greater insight to the issues:
https://gtmetrix.com/reports/www.absoluteasiatravel.com/v6BG7dWF
You need to significantly reduce the number of requests being made. Our optimization tips will help by combining CSS and JS files:
https://generatepress.com/fastest-wordpress-theme/
The other optimization improvements will require you to optimize content such as the images you’re using and question whether everything on the page is required. For example reduce the number of fonts.