Pages damages my file and I cannot open it

Quit Pages from the application menu, and then launch it again while pressing the option key. This prevents it from opening in its previous application state and may allow you to open that Pages document.

However, if Pages crashed while writing that document, it may be permanently damaged, and your only recourse would be to restore the document from your Time Machine backup at a timeframe preceding when Pages quit. Without a Time Machine backup, the document is not recoverable.

Editing a Pages document on a network drive that is not iCloud is risky as you have discovered. In the future, I would do all file I/O locally with Pages, and then if you must, copy it to the network drive. And then, only if that network drive supports Apple document formats and does not strip Finder tags as do Google Drive, DropBox, Box, and probably Microsoft's OneDrive.