At the moment I have CC2531 with ZHA. The problem is not stable, devices continue to disconnect and is not able to find devices which are far away.
I want to move to ConBee II. Do I have to unistall ZHA and delete the db and restart from 0? Or it is just enogh to change the dongle?
You need to repair all of your devices with the ConBee, so restart from scratch.
Ok and another question. During the pair operation should the device near the dongle? or it is enogh that it is near one of the already configured zigbee device?
ZigBee devices should be paired from their final location. The device will decide for itself whether it pairs directly to the router or through one of the already paired devices (only mains powered devices can route traffic between the device and the ConBee).