Internal Server Error after fresh installation

After a fresh installation and while working great, after the installation i received the following message. Please follow below link.

Can anyone help?

No real idea. Perhaps a dns problem problem. Can you resolve dns names? Do you use a firewall? Perhaps you can also solve the errors in in the apache2 configuration.


Thank you for your reply.

It cannot be a dns problem, because letsencrypt is not reporting any error in its logfile.

I am not using any firewall

How will i be able to edit the apache2 configuration?

Can you write something about your system? Normally you can use shell access (ssh) and edit e.g. apache2 configuration in /etc/apache2 .