I cannot connect after enable Firewalld on CentOS7

Solution 1:

It looks like you locked yourself out, as you did not specify that ssh should also be allowed:

sudo firewall-cmd --permanent --zone=public --add-service=http 
sudo firewall-cmd --permanent --zone=public --add-service=https
sudo firewall-cmd --permanent --zone=public --add-service=ssh
sudo firewall-cmd --reload

The guide above seems to assume that ssh is already allowed.

What should I do? The only access to the server was that way for me. I have no physical access to the server.

So at this point the only way to access the server will typically be via the VM console of your hosting provider / virtualisation solution. Almost all providers will allow you access to that console, so you should try to do that. Once logged in via the console, you can then run the above command to allow SSH to regain access via SSH.