Then work on extending human lifespan. This is something the average HN contributor could be making progress towards. E.g. make a YC company working on capability advancement in biotech, or enabling technologies like atomically precise manufacturing.
7 billion years has got to be a bit of a stretch goal, even if you're very bullish on biotech...
Do we know of anything that has that type of lifespan outside of celestial bodies like planets?
M type dwarfs can easily have a lifespan in the main sequence spanning many trillions of years with even their red giant phases estimated to outlasting even the main sequence of stars of our size.
A steller mass black hole's estimated lifespan would of course make even these seem like an eyeblink by comparison.
Both the earth and sun are about ~4.5 billion years old. 7 billion is completely off the charts.