Problem updating firmware

nRF Toolbox disconnects in 10 secs

That's really strange. Have you been able to try from a different phone, in case there is some problem with the Bluetooth LE on yours?

I already connected Puck with TTL now, but trying Espruino IDE it does not work either

No, I'm afraid you have to upload via BLE - there is no serial bootloader at the moment.

The only way would be upload with phyton script (I use it successfully for flashing on ESP8266)

Nothing like that will work for Puck.js I'm afraid. However, what type of computer do you have? If it's not Windows (so you have Web Bluetooth) then you can use this website: https://thegecko.github.io/web-bluetooth­-dfu/examples/secure_dfu_web.html