You are not satisfied with the functionality of the stock firmware.
Where can I find the firmware?
On the official website of the phone manufacturer.
On sites where developers 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. It must have enough memory to fit the firmware.
Remember your smartphone model.
Fully charge your phone. If the battery runs out during boot, the device will no longer turn on.
Download archive with Firmware. Place it on the SD card.
Installing TWRP Recovery
Install the Official TWRP App via the Play Market. And run this application.
At the first start, you need to give consent to future manipulations, as well as consent to granting the Superuser rights to the application. Check the checkboxes and press the 'OK' button.
On the next screen, select 'TWRP FLASH' and give the application root rights.
On the main screen of the application, the 'Select Device' drop-down list is available, in which you need to find and select the device model for installing the recovery.
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.
After downloading the image file, 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'.
The recording process is very fast, and upon completion, the message 'Flash Completed Succsessfuly!' appears. Click 'OK'. The TWRP installation procedure can be considered complete.
Write the firmware to the SD card. Using a PC or laptop card reader.
Insert a memory card into the device.
To reboot in recovery, it is convenient 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 tap 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. This will delete all user data from the device, but avoid a wide range of software errors and other problems.
Everything is ready to start flashing. Press 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 the files were copied. 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 device's memory will begin, accompanied by the appearance of inscriptions in the log field and the completion of the progress bar.
The completion of the installation procedure is indicated by the inscription 'Successful'.