1) Can i use different supersu version?
2) will this delete all my files (like factory reset)?
3) And how can i unroot my phone?
1) Indeed, that actually provides a better rate of success. In my case the SuperSU coming with that package was not working, I tried with a more recent build (Magisk 13.3 is a good alternative) and it worked like a charm.
2) Nope, all your data will be preserved.
3) Just reflash the original boot and you're good to go. If you're using the unroot procedure coming with SuperSU there are chances that your phone will soft-brick (i.e. it will be stuck with the static Blackview logo). In that case reflashing parts of the original rom will fix all your issues and there will be no traces of rooting.
By the way, sometimes the phone will reset recovery to the default one instead of TWRP. In that case just reflash the recovery binary and make sure to boot into recovery mod on your first attempt, that will block the phone from restoring itself, allowing you to flash SuperSU or Magisk, leaving the recovery binary intact in any following reboot.
Also, for those having issues with TWRP in Russian, there is a simple procedure to set it to English or any other language supported by the program. In order to do that, look at the following picture:
Click on Settings (buttons are in the same order, no matter the language), then click on the tab with the little world globe, and it will show you the language selection screen. Tap on whatever language you need and it's done forever, it will never reset itself to Russian from there on.