Hey yael208,
We see that you viewed this page before posting: Manage Health data on your iPhone, iPod touch, or Apple Watch - Apple Support
We also followed the same steps, and noticed that in order to see the "Show All Data" you need to scroll down. Then one that is selected, the Edit will appear in the upper-right corner. We've added that step to what is shown:
"Delete information that you entered
If you entered incorrect details when manually adding health information, you can delete the record.
- Open the Health app and tap the Browse tab.
- Tap a category, like Activity.
- Tap a subcategory, like Steps.
- Scroll down
- Tap Show All Data, then tap Edit in the upper-right corner.
- Tap the Delete button next to the record you want to delete. You can also tap Delete All to delete every record. "
Cheers!