Can't access a website

I been trying to go to a specific website, however it gives me a error messages that says ”Your connection is not private

Attackers might be trying to steal your information from specific website (for example, passwords, messages, or credit cards). Learn more

NET::ERR_CERT_AUTHORITY_INVALID

Automatically send some system information and page content to Google to help detect dangerous apps and sites. Privacy policy ” “This server could not prove that it is specific website; its security certificate is not trusted by your computer's operating system. This may be caused by a misconfiguration or an attacker intercepting your connection.

Proceed to specific website (unsafe)” I click proceed to the website and it gives me a messages that says ´Forbidden

You don't have permission to access / on this server. I would appreciate if someone can help me fix this. I check my anti-virus program to see if it’s blocking it and I couldn’t find anything. I also disable to see if I would be able to go on the website and still nothing. Try to use different internet browser and still nothing.