Just the opposite of your friend’s opinion: the recollected testimony of believers while they were living, but who are now dead, may very well play a part in your life. Remembering them, you and other relatives and acquaintances may believe the gospel and be baptized (see Heb. 13:7). You and they—all whose conversions were the result of your deceased loved ones—were baptized for their sake, not on their behalf. You take their place in the family of God on earth.
Scripture does not teach that dead people are helped by baptism or prayers performed by friends on earth.