@Anonymous
I'm sorry to hear that you are having a tough time with PowerApps at the moment. 15-20 minutes is definitely not normal. Its very hard to troubleshoot an app without seeing it. Maybe you can post a screenshot or two of your PowerApps Studio?
I'd like to ask a couple of questions:
1) When was the last time your App Editor performed well
2) What did you do between the the last time and App Editor performed well and now?
I noticed you said there were 13 pages and 6-14 forms per page. That sounds like alot. I wonder if you are having problems because you are reaching getting close to 500 controls in a single app.
One idea might be to try making an export of the app. Then reload the app into PowerApps and delete screens until the problem no longer exist. It might give you an idea of whether its due to the way you have built your App or if there is some issue with PowerApps.
There is a really good article I suggest you read on how to improve app performance:
https://docs.microsoft.com/en-us/powerapps/maker/canvas-apps/performance-tips