Hi,
In regard to your issue of'windows server update without Internet', I want to confirm that what's the current OS version of your server?
- If the current version of your server is 2016, you can download the latest KB file in the following link from a computer has access to the Internet and share it to the server need to be updated.
https://www.catalog.update.microsoft.com/Home.aspx - If the current version of your server is lower than 2016,
(1)You are in a domain environment and the DC in the domain has SCCM service, you can download the iso file from this service.
(2)You are in a workgroup environment, please download the iso file in another computer and share it to you.
Hope my answer will help you, thanks!