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 on which developers lay out 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 an SD card into your phone to write the 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.
Download the archive with Firmware and place it on the SD card.
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 need to give consent to future manipulations, as well as to give consent to granting 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, 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 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 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 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.
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 location where you copied the files. Press the 'OK' button.
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 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.
After the firmware installation procedure is completed, the 'Successful' message appears on the screen.
Summary: Type: Smartphone, Phablet; Smart Phone OS: Android; OS ver: Android 6.0 Marshmallow; SIM: Dual SIM, Dual Standby; CPU: Quad Core; Processor Speed: 1.3 GHz; Storage: 8GB; RAM: 1GB; External Storage: microSD up to 64GB; Screen Size: 5.5 inches; Resolution: QHD 960 x 540 pixels; Main Camera: 8 MP; Features: WiFi , GPS , Bluetooth , Flash; ...
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