Stay informed with awesome article where you can observe all hints and really helpful suggestions on the matter of site speed problem:
https://www.wpbeginner.com/wordpress-performance-speed/
We recommend to use this bundle of useful plugins that will speed up your site:
-wp-sweep https://wordpress.org/plugins/wp-sweep/
-wp-super-cache https://wordpress.org/plugins/wp-super-cache/
-wp-merge-minify-refresh https://wordpress.org/plugins/merge-minify-refresh/
Also compress all media (images) with TinyPNG service https://tinypng.com/