Greetings, Peninho98. Thank you for posting your question to the Apple Support Communities. We know that keeping track of your completed workouts is important and we’d be happy to show you how to view your past activity.
The following Apple Support article should help you:
Use the Workout app on your Apple Watch
Specifically, we want to call your attention to the section titled: “Check your workout history, Activity history, and your awards”. This section states: “On your iPhone, open the Fitness app. To see details for your workouts, tap the Workout tab, then tap an item.”
We hope this information helps you view your past workout data.
We wish you all the best!