recovery part added to system sdd?

zivshosh said:

The new part is Recovery of 850MB...
Does anyone know what caused it?
is it part of some windows updates...?
Do I really need it?

That is the Windows 10 Recovery partition. It is what you boot to when you choose to boot to Advanced Start-up from Settings > Update & Recovery > Recovery, or when the PC has found a problem at boot and boots to the repair options.
Boot to Advanced Startup Options in Windows 10

If you have just had the update to 1803, then that would have created the recovery partition as part of installing the upgrade.

Can you live without it? Well, only if you have another way to boot to Advanced Start-up. A Windows 10 install usb or a Recovery drive usb can do that for you.
Create Recovery Drive in Windows 10

In a Command prompt (Admin) type reagentc /info to see if the recovery environment is enabled and using that second partition. You could type reagentc /disable to turn off the recovery environment, then it would be safe to delete the partition. Personally I would leave it there in case I needed any Advanced Start-up functions. It's only 850MB after all.

is it part of some windows updates (I am in Windows 10 Pro ver.1803 b17134.112)?

Yes

Do I really need it?

Yes and No
YES: if you want to be able to boot into Windows Recovery Environment for Diagnostic or Trouble Shooting
NO: If you use the bootable Windows Installation USB/DVD to boot from and run Repair This Computer to diagnose or trouble shoot.

zivshosh said:

Greetings
thank you for your quick and informative answers.
I repeat the question if I really need this recovery part since I work with 3 backup programs (Acronis Trueimage, Easeus Todo Backup, Macrium Reflect) all creatig image (clone) of C and even if C is damaged or accidentally formated I can still have it back with these backup programs' rescue disk?
What does the boot to startup gives me in addition?
can I do it if C is damaged and PC doesn't mount?
thank you again

If you make image backups from a known working state, that recovery partition is not that important. You can do everything it does from a usb installation drive.

Presence of the partition is merely for convenience - it does not add anything that cannot be done from an installation drive.

Just saves a little time creating and booting from a usb drive instead.

I always delete them on my 32GB tablet to save space.

PS - I would not bother with Acronis.