When I try to save the website for use in offine mode, the only word shown is undefined.

[SiriusBirius]

No description provided.

[anuknowndeveloper]

the reason why the only word is undefined is because the website needs a web-server to run, because of the way the fetch function in javascript works.
for example, you can try using the features of your ide, such as vscode and atom's "live server" extensions.
another way to solve the issue is to make a node.js server with npm.