I want to point my dns target to my domain name, I’m supposed to add the dns target to Cloudflare as cname, but on my dns I see the domain already mapped to another IP address. Am I supposed to edit that or just create a new cname for all this? I’ll really appreciate any help. Thanks.
I would generally avoid wildcards. Am I right to assume you want your naked domain and your www record to point to terrestrial-triceratops-28ld43h1xc8plrz17u3uk1qy.herokudns.com? If so you should just create to CNAMEs for www and @ and point them to the address. Note that the @ record will be marked as flattened as these can typically not be CNAMEs and will be turned on-the-fly to A records with the applicable IP address.
That is presumably because of your SSL mode which should be one of the "Full"s if you want to use HTTPS. Also, check that your origin is properly configured.
As I mentioned before you need to make sure you have a proper certificate on your server. If you have a certificate but it is not valid you could downgrade to just “Full” but “strict” is certainly preferable from a security point of view.