This error is not related to Cloudflare in any way. It’s coming from Chrome/Google because they found your site to be hosting potential phishing/malware, as can be seen on Google Transparency Report.
That page contains some things on what you could try to get the warning lifted.
Also side-note, but you shouldn’t use the Flexible SSL/TLS setting if you have SSL certs installed. I recommend switching the setting to Full (strict) instead.
SSL/TLS certificate problems result in the “Not secure” categorization that Chrome gives. The “Dangerous” flag occurs when there’s the suspicion of phishing activity taking place on the website. If you believe that to be a mistake, solving this issue would involve contacting with Google, not Cloudflare, and asking them to reevaluate the reputation of your website.