Thanks for reply.
I finally solved my problem flashing back3. 19.5761 firmware.
I have had a strqnge behaviour. When flashing i could see text written, even the 5 suares, and my procedure stop at 4 square. When flashing was done my screen was unable to be readable, all was grey, but i worked because i could see flash light when changing page (refresh every page). Connecting to pc was difficult because you should go for tentative without seeing what you was pressing.
Foetunately i remembered correct position of confirmation when usb cable was plugged into pc
