Hi @UtauyoNASE
Teams requires an internet connection for document collaboration. Teams functionality is tied to the use of internet.
The only thing that works is:
The new offline mode feature in Microsoft Teams lets users browse their recent chats and channels as well as those they’ve pinned without having to connect to the internet.
Cited from https://mspoweruser.com/use-microsoft-teams-in-offline-mode/
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If this is helpful please accept answer.