Hello @anonimfan, thank you for letting us know about your concern, could you please answer the following questions to get a better resolution for this:
1 - What kind of device and OS do you have?
2 - Have you updated to the latest Brave version? If this is a desktop computer (found at brave://settings/help) to download the most recent one (https://brave.com/download/).
3 - A screenshot of the issue (if possible).
Also, these articles can be helpful to you: Picture in Picture , Pip and https://www.techrepublic.com/article/how-to-add-the-picture-in-picture-extension-with-the-brave-browser/
Hope that can help you. Regards.