Adobe compatibility with iMac 2013

What version of macOS are you running? You may still be able to use an older version of Photoshop with your subscription.

Sounds like you have an iMac with an nVidia video card. Yes, your video card is too old and underpowered to support GPU acceleration in Photoshop.

This article has more info:

https://helpx.adobe.com/photoshop/kb/photoshop-cc-gpu-card-faq.html

When you ask a question you always need to provide some basic information
-Forum quick start https://community.adobe.com/t5/Community-Help/ASK-Forum-Success-Guide-Efficiently-using-the-forums/td-p/4791542
-https://community.adobe.com/t5/Get-Started/Questions-you-need-to-answer-to-receive-better-help/td-p/6199470
-https://community.adobe.com/t5/get-started/how-to-post-and-get-your-issue-resolved-or-what-do-you-need-to-know-to-solve-my-issue/td-p/11178657?page=1