Bluetooth with Pi 3b+

Hello, so my problem is that I cant get my BT speakers (soundbox color) connected to my pi. I did the sudo apt get update a2dp thing, but I still cant get it connected. Paring and trusting works thou.
I am using the built in bt device from the pi, is that maybe the problem?

Well it should work, maybe not as stable as external dongle but it should work.

Did you change the audio output to alsa/bluetooth?

Yes I changed the audio setting.
I just checked if I really did it and tested the bt connection and now it seems to work, even the audio output is there.