Slowness can be either site or server related. Gtmetrix is a good resource to use to diagnose front-end ( site ) related issues, a quick scan for your site at https://gtmetrix.com/reports/tourismnewsbd.com/WxGuwzit ( click on Timeline ) shows you have lots of images loading,the CSS files for your site also takes a while to load. You should consider optimizing images with a plugin such as WP Smush.it, combining multiple CSS files into one, using a caching plugin such as W3 Total Cache or WP Super Cache, using gzip compresssion and adding caching headers. If that does not resolve your issue then there could be something else wrong on the server site, the link below should provide some more insight into optimizing WordPress.
https://wpaid.net/wordpress-optimization/
Hope you get your issue resolved.
