Mac os mojave

> Says it's been damaged

That is usually caused by expired certificates when you have an old macOS installer in /Applications. Trash it and download a new on (or turn the Mac's system clock several years back).

You can get it here: How to download and install macOS - Apple Support

But why? What version of macOS are you running now?

The mojave download doesn't work from this page. Says it's been damaged. Do you have another link?

Thanks!

Susan