My touchscreen completly stop work after load wrong firmware

You may have turned off touch screen in the setting some how, or the wires. connected to the screen might have came off some how. You can go to staples and they should be able to fix it for you or you can call the company and they could tell you how to fix it.

Did you ever think about if your screen is dirty? That could be the reason, because touchscreen does not work for me when it is dirty. Maybe you use it too much, and it has too many finger prints. This question is vague, so i do not know if you did this or not, but if you didn't then wipe your screen with a special towel meant for wiping touch screens. If that doesn't work, then go to a store to get if fixed. Personally, I think Dell devices are never worth buying because there is always something wrong with them, and i would replace it, but if you really love that tablet then bring it to a store to see if it can be fixed.