Entire website disappeared

Hi there,

Tonight I was updating my WordPress blog with a new page. By accident I used a dot in the page name.
From that moment my entire website disappeard and only give an error message at any page I try to enter at https://www.mywebsite.com. (Error message is “Internal Server Error
The server encountered an internal error or misconfiguration and was unable to complete your request.”
)
I even get this error message when trying to enter the wp-admin directory, so I can’t even access the WordPress Dashboard. Any ideas how to solve this problem?

Thanks in advance,

Hans