Hi there @Axel_TTa,
Welcome to the Community! Happy to help!
Users get a second email confirming their subscription to your brand’s marketing if the list connected to your signup form is set to Double opt-in. If you change your list setting to single opt-in instead, you can do so on in the List’s settings page. Then, users will be immediately added to your list and sent to the flows the list is connected to. Users will only get a subscription confirmation email once for ever double opt-in list they sign up to and then never again. It should be noted that it is considered best practice to set your list to double opt in. I’d investigate these threads to gain more insight on the topic!
Finally, I’d recommend checking out these resources to help you learn more about Klaviyo and build a strong foundation.
Hope this helps!
-Taylor