I'm very happy 

After spending a lot of time trying to figure out how to install an original firmware using the dload method, I managed to find a guide that explains how to do it and today I will report the main steps:
First of all, we need the Service Firmware of our device. It can be found here http://androidhost.ru/search.html. From this site you have to search ane-l01 (or ane-l21 if your device is dual sim). So download the relevant firmware (p.s. I saw there aren't the latest firmwares, in my case I installed the 8.0.0.149 version, not the 8.0.0.154 ).
Then extract the "Software" folder and copy the "dload" folder (with its contents!) to the external sd card.
Finally, enter to the project menu from dialer typing *#*#2846579#*#* ==> Software Upgrade ==> SdCard Upgrade.
Wait for the installation and before configuring the device enter in Recovery Mode (from the phone off, VOLUME-UP + POWER ON) and make Wipe Cache Partition, Wipe Data/Factory Reset, Reboot System Now.
After spending a lot of time trying to figure out how to install an original firmware using the dload method, I managed to find a guide that explains how to do it and today I will report the main steps:
First of all, we need the Service Firmware of our device. It can be found here http://androidhost.ru/search.html. From this site you have to search ane-l01 (or ane-l21 if your device is dual sim). So download the relevant firmware (p.s. I saw there aren't the latest firmwares, in my case I installed the 8.0.0.149 version, not the 8.0.0.154 ).
Then extract the "Software" folder and copy the "dload" folder (with its contents!) to the external sd card.
Finally, enter to the project menu from dialer typing *#*#2846579#*#* ==> Software Upgrade ==> SdCard Upgrade.
Wait for the installation and before configuring the device enter in Recovery Mode (from the phone off, VOLUME-UP + POWER ON) and make Wipe Cache Partition, Wipe Data/Factory Reset, Reboot System Now.