You are not satisfied with the possibilities of the stock firmware.
Where can I find the firmware?
On the official website of the 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 your SD card into your phone. An SD card is needed to write firmware to it.
Determine your smartphone model.
Fully charge your device's battery.
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 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, click 'Select Device', and select 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, 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 can be considered 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 errors in the software, as well as other problems. Press 'WIPE' on the home screen.
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 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, 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; Band: LTE, 3G (UMTS), GSM 900, GSM 1800, GSM 1900; Platform: Android; Operating system: Android 7.0; Processor: Qualcomm Snapdragon 821 MSM8996; Number of processor cores: 4; CPU frequency: 2 350 MHz; Graphics processor: Adreno 530; RAM: 4 096 MB; Extendable Memory: 32 GB; Memory card slot: yes; Type of memory card: microSD (TransFlash), micro SDHC, micro SDXC; Storage expansion: 256 GB; Dimensions (H/L/W): 148.9x71.9x7.9 mm; Weight: 163 g; Housing material: Metal and glass; The number of SIM-cards: 2; Type of SIM card: nano SIM; Fingerprint ID: yes; SOS button: no; Water protection: yes; Impact-resistant housing: yes; Color screen: yes; Curved screen ...
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