The human brain cannot live forever.
Eventually as we age the brain cells start dying and if we were to live forever our brains would turn to mush anyway.
You can help your brain survive much longer and keep the brain healthy by doing mind games, taking brain supplements, eating plenty of foods with vitamins.
Stay active and keep your mind active as well and your brain can stay healthy and you may not get dementia or other brain issues.
However you might still get dementia or other brain issues when you have someone or somebody in your family who has or has had dementia or other brain issues.
As of now it's impossible for a human or human brain to live forever and it's very unlikely that a human would ever be able to live forever.