@Gen Genada Mahinay
In the "Vitals" Section, under "Death", select "Edit".
That will bring up a "Pop-Up" (ie. "Modal") 'Window'.
There, select "Living"; and, then, "Save" - done.
I hope this helps.
If you did not create the person, then sometimes you have to contact Familysearch to have a deceased person marked as living. It is important to do as living people are kept private and we want to protect that privacy.