You are not satisfied with the possibilities of the stock firmware.
Where can I find the firmware?
On the official website of the phone manufacturer.
On specialized services where users post custom or official OS.
What should be done before installing the firmware?
Back up your contacts and user data and transfer it to your computer.
Insert SD card. An SD card is needed to write firmware to it.
Determine your smartphone model.
Fully charge your phone. If the battery runs out during boot, the device will no longer turn on.
Find and download the archive with Firmware.
Installing TWRP Recovery
Install the Official TWRP App via the Play Market. And run this application.
When you start the application for the first time, you must agree to install the firmware, as well as agree to grant the application Superuser rights and click the 'OK' button.
On the next screen, select 'TWRP FLASH' and give the application root rights.
On the main screen of the application, click 'Select Device', and select your phone model.
After selecting a device, the program redirects the user to a web page to download the corresponding image file of the modified recovery environment. Download the suggested *.img file.
When the file is loaded, you need to 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.
Now 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 is now complete.
Copy the required files to the memory card. Using a PC or laptop card reader.
Insert a memory card into the device.
To reboot into recovery, you need to enter the menu accessible by pressing the button with three stripes in the upper left corner of the main screen of the application. Select 'Reboot' and then click on the 'REBOOT RECOVERY' button.
Firmware via TWRP
Before flashing, you need to delete all user data from the phone, this will avoid many problems. press 'WIPE' on the home screen.
You can start flashing. Click the 'Install' button.
The file selection screen appears. At the very top is the 'Storage' button, select the location where the firmware file is located.
Select the storage to which the files were copied.
Select the firmware file 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 damaged files during recording.
The procedure for flashing the phone will begin, accompanied by the appearance of inscriptions in the log field and the movement of the progress bar.
After the firmware installation procedure is completed, the 'Successful' message appears on the screen.
Summary: OS version: Android 6.0; CPU: MediaTek MT6580, 1300 MHz; Processor cores number: 4; RAM: 1 GB; Built-in memory: 8 GB; Video processor: Mali-400 MP2; Memory card slot: yes, volume of up to 32 GB; Multi SIM mode: alternate; SIM-card amount: 2; Case type: classic; Case material: metal and plastic; Height: 150 mm; Width: 74 mm; Thickness: 9.9 mm; Weight: 350 grams; Diagonal: 4.7"; Screen type: colored IPS, sensor; Sensor screen type: multitouch, capacitive; Screen size: 1280x720; Number of pixels per inch (PPI): 312; Aspect Ratio: 16:9; Automatic display rotation: yes; Scratch-resistant glass: yes; Sensors: illumination sensor, approaching sensor, fingerprint scanner; Rear camera: 8 MP; Flash: ...
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