I found this topic
And added rules to bypass WAF for requests with google ASN which is 15169.
After that this tool
https://pagespeed.web.dev stopped yelling about 403 response. And shows results sometimes, but mostly it ends up with timeout 2 minutes. But If I look at loading time in devtools in Chrome I get 9.5 seconds.
Did I miss something? Could anyone point me out please?