The OS does not match the system requirements of the smartphone.
Where can I find the firmware?
On the official website of the manufacturer.
On specialized services on which developers lay out custom or official OS.
What should be done before installing the firmware?
Create a backup copy of user data, contacts and photos and transfer it to your computer.
Insert an SD card into your phone to write the firmware to it.
Find information about your smartphone model.
Fully charge your device's battery.
Download the archive with Firmware and place it on the SD card.
Installing TWRP Recovery
Download and install the Official TWRP App from the Play Market.
When you start the application for the first time, you need to give consent to future manipulations, as well as to give consent to granting the application Superuser rights and click the 'OK' button.
In the next screen, select the item 'TWRP FLASH' and provide the application with root-rights.
On the main screen of the application, select 'Select Device', and find your phone model.
After selecting the phone, the application will redirect the user to a web page to download the modified recovery environment image file. Download the proposed *.img file.
When the file is loaded, return to the main screen of the Official TWRP App and press the 'Select a file to flash' button. Select the file downloaded in the previous step.
Press the 'FLASH TO RECOVERY' button and confirm your choice, press 'OK'.
When the message 'Flash Completed Succsessfuly!' appears. Click 'OK'. The TWRP installation procedure can be considered complete.
Write the firmware and other necessary files to the SD card. Using a PC or laptop card reader, it will be much faster.
Insert a memory card into your phone.
To reboot into recovery, you need to use a special item in the Official TWRP App menu, accessible by pressing the button with three stripes in the upper left corner of the main screen of the application. We open the menu, select the 'Reboot' item, and then click on the 'REBOOT RECOVERY' button. The phone will reboot into the recovery environment automatically.
Firmware via TWRP
Before flashing, you need to clear the 'Cache' and 'Data' sections, press 'WIPE' on the main screen. You will delete all user data from the phone, this will avoid software errors and other problems.
Now you can start flashing. Click the 'Install' button.
The file selection screen is displayed. At the very top is the 'Storage' button, select the location where the firmware file is located.
Select the location where you copied the files. Press the 'OK' button.
Find the file we need and click on it. A screen opens with a warning about possible negative consequences, you need to check the item 'Zip signature verification', which will avoid using corrupted files when writing to the phone's memory sections.
The procedure for writing files to the phone's memory will begin, this is accompanied by the appearance of inscriptions in the log field and the movement of the progress bar.
The completion of the firmware installation procedure is indicated by the inscription 'Successful'.