What can we do better?

[RobinK]

Could whoever is in charge of the web server try this, please? It's from MyBB Documentation - Setting up HTTPS. And if you open a browser console and analyse the content delivered when you load https://www.tost3.com/, you will see that (at least, I didn't check any further) the CSS is delivered via http instead. This would explain the weird look of the site, because that's what the site looks like without the CSS.

Removing mixed content
Mixed content (insecure content) occurs when the initial page is delivered over HTTPS, but includes content (such as images, videos, etc.) downloaded through insecure HTTP, limiting the security benefits of HTTPS (read more).
Templates and CSS
Some resources, like images, CSS or JavaScript files might be loaded through your MyBB theme’s CSS files (Templates & Style → Themes) and templates (Templates & Style → Templates). Those are usually located in the headerinclude template (Ungrouped Templates). You can also use the Search/Replace utility to find all occurrences of 

Code:

http://

 to replace it with 

Code:

https://

, making sure these resources work correctly under the new address first.