Installation issue

You will want to start with a fresh download of the Mojave Installer from the Mac App Store.

If you already have an app called Install macOS Mojave in your Applications folder, delete it and empty the trash. Then go the the App Store and download macOS Mojave again.

Then follow the instructions in either of these support documents below:

How to upgrade to macOS Mojave - Apple Support

How to create a bootable installer for macOS - Apple Support

If it is damaged then there is no way you can install it. move the Install macOS Move.app to the Trash, empty the Trash.

connect your mac to your router via cable, Restart your mac go back to the App Store Mojave page and download Mojave again.

Don't use the mac whilst the mac is downloading.