Hi Torben,
As already mentioned, a Bluetooth-based connection between the keyboard/mixer and active speakers is not recommended for live playing. Even with the latest BT versions (e.g. 5.3), the latency is usually over 30 ms.
There are special wireless AUDIO transmission systems for this purpose. However, professional systems of this type are usually quite expensive.
At its simplest, you can use a digital system meant for guitar/bass. (For a Stereo signal you will need two of them.) These have latencies of only 3 - 5 ms. However, these systems usually work in the frequency range of 2.4 or 5 GHz, which is also used for WiFi (Wireless LAN) and Bluetooth and is therefore relatively susceptible to interference. In addition, systems intended for instruments should be checked to see whether they are suitable for a line level input signal.
Best regards,
Chris