Error 520 & SSL Handshake

Hi !
Ive recently had SSL handshake error (1-2x ) , but mainly Error 520 , unknow error.
Ive talked to my developer, and he said my ssl was expired. Ive never purchase any ssl from my hosting. Ive always use the free basic ssl from cloudflare.

Im not sure what the developer did, he log into my cloudflare and all was working. He did mention something about my ssl was expired ?
What should I do, Can I just use the cloudflare free ssl vs purchase new one from hosting?

Using Cloudflare SSL to front an origin service that doesn’t have SSL is not recommended as it means your traffic is not encrypted between Cloudflare and your server, but your users are deceived into thinking their connections are secure.

You should always install a valid SSL certificate on your origin even if using Cloudflare SSL. Free certificates can be obtained from LetsEncrypt or, if you will always use the Cloudflare proxy, a Cloudflare origin certificate.

For checking the Cloudflare edge SSL certificate you can give the domain name.

Thanks. I will consider that. Somehow my developer shut off the SSL and my website seem to me working now
Do you know , where I can shut off this feature? I cannot seem to find it on cloufflare.