Do I need to cancel one booking if I created two identical orders?
Yes. To cancel, you need to write to the Care Service chat and provide the order number you wish to cancel. We will resolve the issue within a few minutes.
You can find the chat on the website in the lower right corner of the screen:

In the app, the chat is located in the bottom block in the middle:

Sometimes the airline may cancel both bookings if it finds identical orders, so be careful and avoid duplicates.