Problem with connection to nextcloud via client

Hello, i have a problem to connecting my nextcloud client to the server. I have a macbook, the latest nextcloud and the latest client. I can access the server via https, on the port 80 and 443. My domain where i have nextcloud is ( -port 80/443.
Ive tried to connect with https and http, with port 80,443 and without port, with and without www, and nothing worked. If i enter the server address the server was found and it redirects me to the browser where i can login and verify the access for the client. Everything works (the login to) and after 30 sec i get an error: the connection failed.
And i dont know why connection failed/is lost. The server is accessible and online, and i use shared hosting for nextcloud (its for home use-for 6 users only).
Why i cant connect nextcloud to the client, please help.

Bildschirmfoto 2020-11-26 um 20.21.44

Due to the fact that the majority of the users most likely cannot read your language, it would be nice if you could add translations of the displayed messages under each of your screenshots :wink: