Three mistakes! Caching does not work

1. It looks like you have another caching or optimisation plugin installed and enabled.
2. You need to add write access to the .htaccess via permissions on your control panel file manager or by manually adding the contents of the text area to your .htaccess.
3. The main caching features requires you to use a web host that uses LiteSpeed server.

Not via WordPress plugin, but the control panel supplied by your hosting provider.

Are you using cPanel or any other control panel?

What type of hosting are you using?

WordPress.com or WordPress VIP?

Because they are hosting you, you are limited on the plugins you can install and access to the hosting platform.

Your site should already be statically cached via your hosting provider.

What caching features are you looking to use?

How many plugins do you have installed?

TTFB it very slow, you need to investigate what’s causing the delay. Are you able to install https://en-gb.ww.wp.xz.cn/plugins/query-monitor/ and share the results? Please hide any information that may be private.

You also have 154 requests, it’s best to combine CSS and JS files. I can see one of your JS files is 464.9KB, that’s pretty large. You must have a lot of plugins bloating your page.

To really optimise your site, you might have to move away from WordPress.com.