Cloudflare says "Your SSL/TLS encryption mode is Full" but website is not loading on https

cloudflare says “Your SSL/TLS encryption mode is Full” but website is not loading on https.
website is

Rather slowly, but it is loading on HTTPS

You do have a “mixed content” issue though. Use the search here for that keyword for more details on how to fix this on your server.

I m getting this message on my wp dashboard

Detected possible certificate issues

Really Simple SSL failed to detect a valid SSL certificate. If you do have an SSL certificate, try to reload this page over https by clicking this button:

Reload over https

The built-in certificate check will run once daily, to force a new certificate check visit the SSL settings page. Really Simple SSL requires a valid SSL certificate. You can check your certificate on Qualys SSL Labs.

That would refer to your server. You need a certificate there too. Have you configured your server with a certificate?

i got the ssl certificate from cloudflare.

You mean you installed an Origin certificate on your server?

Assuming your server IP address ends in 44, it would not appear that you have configured a Cloudflare certificate. There only is a self-signed certificate, which means your encryption mode cannot be better than just “Full” and is not properly secured.

You should install a proper certificate and change that to “Full strict”.

i have hosting on go daddy. i changed the name servers of go daddy with the name servers given by cloudflare.
Do i need to anything more to get a ssl certificate?

cloud flare ssl test shows that i have a valid ssl certificate

Please read what I wrote earlier. You need two certificates and you only have one. You should configure a proper certificate on your server.

do i have to buy it?

No, just get an Origin certificate

how and from where?

which private key type should i choose RSA or ECDSA

I would try both and pick whatever works. RSA probably.

how do i save private key and certificate to my web server

Please use a search engine. That really is a generic question, not specific to Cloudflare.