I, Wallfacer's Assistant

Lin Sen traveled to the Trisolaran world, and time moved into Crisis Era Year 7, where human society was increasingly challenging, but Lin Sen was startled to discover that his original self turned out to be Logic's childhood friend.
Having read 'The Three-Body Problem' in a previous life, there were too many regrets in the book; becoming a Wallfacer's Assistant with Logic's help seemed to be the best way to make amends for those regrets.
How could Lin Sen, who had a clear understanding of the plot, help humanity survive in the Trisolaran crisis? What was the deeper cosmic landscape of cosmic sociology like, and was it all just darkness...
Human civilization was like a small boat drifting in the vast sea of the universe, and a mere wave could capsize it. How far could it sail?
The early stages are basically in accordance with the original text, friends who have not read 'The Three-Body Problem' can rest assured in its use.