Please have a look at https://openwrt.org/docs/guide-user/network/traffic-shaping/sqm for instructions and at https://openwrt.org/docs/guide-user/network/traffic-shaping/sqm-details for the details.
Also please follow the recommendations given in https://forum.openwrt.org/t/sqm-qos-recommended-settings-for-the-dslreports-speedtest-bufferbloat-testing/2803 for how to configure the dslreports Speedtests and how to link in the results here.
If you have anymore specific questions I am happy to help....