LAN Configuration ... No Internet access

My NAS (My Book Live Duo) is connected to a NetGear device with an ethernet cable (RJ45). The NetGear “speaks” with my modem.
The Windows PC has full access to the NAS via the WiFi; no trouble. And the PC as well has Internet access via the modem.

However, when I enter the NAS’s settings via the browser interface, then the “LAN Configuration” says there is no Internet access.

At present the date-time settings in the NAS are completely wrong. Manual settings are no longer possible (latest year is 2020 in the drop-down menu), and NTP is blocked since then NAS does not see any Internet. And my backup-system B4A can no longer restore due to weird time-stamps. This is somewhat annoying.

Q: Could anyone outline how to tell my NAS where to get find the Internet?