The last time I had install issues with Adobe, they provided install support for free! It’s not cheap software and the support for installing was included.
Go to the Adobe website on safari browser click onto the Mac version of photoshop it should download & in downloads after the download has completed you should find a .dmg double click the dmg file you may have to go to file vault & unlock with your computers password you should be guided through the process & drag the photoshop file into your application folder. When you open photoshop for the first time on your machine you will be given a 30 day free trial. After that you will need to purchase a licence to continue to use the program. I wish you all the success in the future.
Simply download Photoshop from the Creative Cloud website and install it on your desktop.
Go to the Creative Cloud website, and click Download. If prompted, sign in to your Creative Cloud account.
Download Photoshop from the Creative Cloud website
If you’re using Windows, you may be prompted to save the downloaded file. If you’re using macOS, you may be prompted to allow the download to take place.
Double-click the downloaded file to begin installation.
Follow the onscreen instructions to complete the installation.
On successful installation, the Creative Cloud desktop app launches at the same time as Photoshop.
When you start the Photoshop download, confirm the download in your browser. After downloading the Photoshop_Installer.dmg file to your Mac, click the Downloads folder on the Dock and run it. After the Installer is mounted on your system, double-click the logo to install Adobe Creative Cloud and Photoshop.
Go to Finder > Applications > Photoshop 2020 (Right click on Photoshop) > Choose Show Package Content > macOS, and then try to launch Photoshop from there.