Why does Spotify and YouTube switch to AirPlay instead of Huawei FreeBuds Pro 3 on iPhone 11?

Hi, I have an huawei freebuds pro 3 headphones and an iphone 11. I can connect my headphones to my phone and there is no problem with taking phone calls either on whatsapp nor facetime calls. I am also using this headphones with mac and ipad.

After connecting headphones to iphone 11, i can see that sound is on bluetooth device. However, when play something from spotify or youtube, airplay deletes headphones and starts playing on air.

how can i fix this problem?