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 sites where third-party developers post custom operating systems.
What should be done before installing the firmware?
Create a backup copy of all personal information: contacts, photos and transfer it to another 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.
Download archive with Firmware. Place it on the SD card.
Installing TWRP Recovery
Download the Official TWRP App to your phone from the Play Market. And install this app.
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 download is finished, you need to return to the main screen of the Official TWRP App and click on 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.
Transfer the necessary files to the SD memory card. Using a PC or laptop card reader, it will be much faster.
Insert a SD memory card into the phone.
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.