How to complete 5,000,000 lifetime meters in level 11?
As @TimmyJim said, just keep running.
According to Cole Stobbs, the average running speed in Temple Run 2 is 12.5 m/s.
Dividing 5,000,000 meters by 12.5 gives us a total of 400,000 seconds. According to Wolfram Alpha, this converts to 4 days, 15 hours, 6 minutes, and 40 seconds of total playtime to unlock the achievement.