Hello angelinerann18,
I understand you're having an issue on your iPhone 11 involving the "Slide to Power Off" function. I'll try to do the best I can to help you.
I would recommend running a force-restart on your iPhone. None of your data will be lost during this procedure. To do so, press and quickly release the Volume Up button. Then press and quickly release the Volume Down button. Finally, press and hold the Side button until you see the Apple logo.
If you need more information, read this article: If your iPhone, iPad, or iPod touch won't turn on or is frozen - Apple Support
This should solve the problem. If you have any other issues, feel free to ask about them!