The phone shuts down and restarts for no apparent reason.
The phone began to slow down a lot.
You are not satisfied with the functionality of the stock firmware.
Where can I find the firmware?
On the phone manufacturer's website.
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 another medium.
Insert your SD card into your phone. An SD card is needed to write firmware to it.
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
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 need to give consent to future manipulations, as well as to give consent to granting the application Superuser rights and click the 'OK' button.
Going to the next screen, select the item 'TWRP FLASH' and provide the application with 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.
After adding the image file to the program, click the 'FLASH TO RECOVERY' button and confirm your choice, click 'OK'.
When 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 phone.
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 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.
Everything is ready to start flashing. Press the 'Install' button.
The file selection screen appears. At the very top there is a 'Storage' button for selecting an SD card.
Select the location where the files were copied. Press the 'OK' button.
Find the file we need and click on it. A screen opens with a warning about possible negative consequences, as well as the item 'Zip signature verification'. This item should be checked by placing a cross in the check-box, which will avoid using damaged files when writing to the phone's memory sections.
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.
The completion of the installation procedure is indicated by the inscription 'Successful'.