You just need to give it time. A couple days is no where near enough. Google will move your site over to HTTPS in its search index one page at a time. Depending on the size of your site, the process could take up to a year. See HTTP to HTTPS: Wait for new sitemap to be indexed?
In addition, rankings sometimes worsen in Google when redirecting to HTTPS. ...
On May 18th you changed your nameservers from:
Old nameservers resolve your name as:
;; ANSWER SECTION:
davidkim2020.com. 2h40m IN A 220.127.116.11
The requirement for an SSL certificate is determined by the domain you're redirecting from, as that's the domain that will be serving up the redirect itself.
In short, the server behind your "from" domain needs to have a valid SSL certificate to serve up a redirect from https. If you're using a "redirecting service" like the "domain forwarding" option ...
If you don't have a valid SSL certificate, then it's not possible to redirect HTTPS to HTTP without a warning.
To properly issue the redirect, the site needs to have a valid SSL certificate. And if the site has a valid SSL certificate, then at that point it usually makes more sense to just serve the site over HTTPS.