every time I want to install the theme, this message appearsThe link you have followed has expired.
Please try again.
You need to go to your item downloads page on ThemeForest and download just the installable wordpress theme zip file. Then you can upload that to WordPress. If you have issues with that, it means there is an issue with your WordPress installation.
I have installed wordpress several times again and the same error keeps coming up
You need to either contact ThemeForest support for help with item downloads, or you need to reach out to your web host and ask them for help with your WordPress installation. This is not a theme-related issue.