Last week, the Vodafone technician arrived and replaced the device with a brand new one. And today my laptop cooler finally arrived. With two 144mm quiet big fans(powered with an usb cable directly connected to a wall pluged socket), this is working perfectl. The device is no longer hot, not even warm when touched even under heavy load.
I strongly recommend people who use a lot of Internet and have a lot of connected deviced in the house (multip computers smartphones laptops) to try this. No more disconnects, lag and packet losses.