I was doing whonix gateway updates and updater ask me if i want to replace or leave grub config. I choose to leave old config. Does my decision was not good ? How it can effect my security ?
Please see, if this answers your question:
My question answered, but now i know that i make mistake. The file was coming from whonix, i think. Can i recall that action again ? apt-get update && apt-get dist-upgrade now not give me opportunity to choose 
the file was called /etc/default/grub.whonix
I don’t think so. But you’re lucky, that file /etc/default/grub isn’t security relevant yet. And you can manually undo that action.
https://github.com/Whonix/Whonix/blob/master/whonix_shared/etc/default/grub.whonix
Good to hear 
So I just need to replace that old file with this https://github.com/Whonix/Whonix/blob/master/whonix_shared/etc/default/grub.whonix and nothing more ?
Know now
If you change this file, run 'update-grub' afterwards to update