Hello Hugoagogo52,
We're happy to help you with removing the activity data from your Apple Watch. On the companion iPhone, open the Health app, then go to "Show All Health Data". Tap the activity you want to remove, and then tap "All Data". Scroll down to "Show All Data", and tap "Edit" in the upper right corner. Select the date of the activity you want to remove, tap the red circle to the left of it, and tap "Delete" on the right side. When you're finished, tap "Done" in the upper right corner. Let us know if you have any questions.
Have a great day!