Delete queue for all devices

I had some problem on adding messages to queue, and now I have around 100 messages for each device in queue.
Is there any way of remove all queue for all devices?
I did write some bad script that removes queue for one device but maybe there is better way …

Yes you can through the API (per device), please see the following endpoint:

DELETE /api/devices/{devEUI}/queue

Or you can empty the device_queue table within the LoRa Server database.