Setting permalinks

I have installed and activated WP Fastest cache. So far so good. Then I went to its settings, selected pretty much every option and clicked on ‘submit’. After this, I don’t see a change in the settings, also the speedtest on https://www.isitwp.com/free-website-speed-test-tool-for-wordpress/ results in the same issues.

In the settings it is stated that I need to set permalinks. What and how do I need to set this?

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