How to for a newbie

[Luke]

Where I can find a step by step instruction for the update process?

I found an SD card and have burned there Debian before, so — I need to download mate image from here (https://github.com/ayufan-pine64/linux-b...tag/0.7.19 what file I need to choose?) and burn it to sd card?

For the Pinebook you want this image. It will run off of the SD card. If you want to flash the image to eMMC then you can either 1) get the Pine64 installer and download the SD -> eMMC image and then update the image (follow instructions on ayufan's git) to the newest pre-release or 2) modify the SD->eMMC installation image so that it flashes the newest pre-release.