Redirecting issues

For example, I have that issue here: https://tecnologiaegadgets.com/aproveite-praticidade-do-armazenamento-em-nuvem-para-sua-empresa-de-ti/3324/

But https://www.tecnologiaegadgets.com/aproveite-praticidade-do-armazenamento-em-nuvem-para-sua-empresa-de-ti/3324/ (with the www. in the begin) does not have any problem.
The problem looks like it is when I write the urls without www.

Can you help me with this?

You probably have a custom redirect from the https:// to https://www. Because it redirects to http instead of https, it keeps redirecting the https site to http, and Really Simple SSL redirects back to https. This causes the loop.

If you remove the redirect, the loop is gone. It is probably in your .htaccess file, or in a redirect plugin.

Where do you see the redirect from the https:// to https://www. and http instead of https?
Here I only see it redirecting to the same https:// page:
https://screenshots.firefox.com/s23kJoNgd67FRAeh/redirectdetective.com

As the loop only occurs when not loaded over http, and Really Simple SSL redirects the same for both www and non-www, this is a custom redirect by something else on your site. The most common causes are listed here:
https://really-simple-ssl.com/knowledge-base/my-website-is-in-a-redirect-loop/

I am using Cloudflare on my website.
Can you tell me which setting should I activate or deactivate on Cloudflare to no cause any problems with Really Simple SSL?

Here are instructions on how to use CloudFlare with SSL:
https://really-simple-ssl.com/knowledge-base/ssl-cloudflare-really-simple-ssl/

If applying the above does not help you can check if the article below applies to you:
https://really-simple-ssl.com/knowledge-base/www-not-redirecting-non-www-cloudflare/

you can find a lot of information on the website. Most issues have been documented in articles there.

I have a certificate from Comodo.
You can see it here: https://sslanalyzer.comodoca.com/?url=tecnologiaegadgets.com
Should I select “Full SSL” or “Full Strict SSL”?
Which of this setting should I enable: https://screenshots.firefox.com/1efY58RqmlrwElhx/www.cloudflare.com ?

As described in the article, if you have your own certificate, you can choose Full SSL. But I expect your non www redirection issue to be caused by a redirect on your own site.

But should I select the “Full SSL” or the “Full Strict SSL” option on CloudFlare?

You can select Full Strict SSL, as you have a valid SSL certificate on your own site.

Thanks for the help!