my macOS mojave didn't update because file is damaged. All I see is an update. What can I do?

If you get a corrupted message...

Naw, not damaged, it's just that you have an old copy already in Applications, there are 2 cures...

Disconnect from the Internet & set the Date back to 2014, then you can run the Install MacsOS Mohave App in Applications, so expired Certificates are not expired.

Or... trash the Install MacsOS Mojave.app in Applications, empty trash & restart, then a new copy of a more recent version can be downloaded..

I think I can help you. It appears that you hav two issues going on. The first appears to be that in order to install Final Draft you need to upgrade your operating system, not just update it. It is important to understand the difference between updates and upgrades. An update is when we install a newer version of the same operating system. An upgrade is when you install a newer  operating system such as upgrading from Catalina to Big Sur. Most likely you have installed the downloaded update unless you have received a message that says it could not be installed. Keep in mind that what you can upgrade to is dependent on the year and model Mac you have. Since we do not know what year and model Mac you have, we can't tell which upgrade, if any, your Mac will accept. Upgrade links may be found in the Apple App Store. I hope this information is helpful in clearing up any confusion.

Great, take care my friend... it wasn't really damaged, just an older file that lost certification, but the newer one will several updates included over the one your deleting.