Hi Iceman1965,
We understand you have questions about deleting the Fitness application on an iPhone. We're happy to help.
To start, if you currently have an Apple Watch paired with the iPhone, you'll need to unpair that to be able to delete the Fitness app. You can remove it from your home screen, but you cannot completely delete it from the device while an Apple Watch is paired as that app is needed to store the activity data from the watch. You can find the steps to unpair an Apple Watch here: Unpair and erase your Apple Watch
Once the watch has been unpaired, you can proceed with deleting the Fitness application. Delete apps on your iPhone, iPad, and iPod touch
If you re-pair the watch at a later time, it will automatically install the Fitness app during the setup process. If you do this, you'll be starting the Fitness app off on a clean slate. Any data that was saved in it from before you unpaired the watch and deleted the app would not come back.
We hope this helps. Cheers!