Thank you for contacting Microsoft Office Community and We will be glad to assist you with your concern. I understand that the PowerPoint application is slow when playing presentation or editing the presentations.
I have a couple of questions before we proceed.
1. Does this occur to a specific presentation or even with other presentations?
2. Does this occur even when creating a sample presentation?
3. Are you able to work with other Office applications apart from the PowerPoint?
Let me help with you. As you have already re-installed the Office suite, follow the steps to determine and fix the issue.