This is not strictly true. You can still make deep connections later in life. Very true that it takes effort though, and not as easy as when you are younger. Not impossible though.

Its reversable. I started going back to the gym at 39 and am stronger now than i was when I was younger. I have knee pain, but thats a weight issue honestly.

Lift wieghts and or do some other physical activity. Its good to have two hobbies; a mental one and a physical one. The muscle you build now will be with you for the rest of your life, and its mucb easier to do it now than when you are middle aged like me.

Dont focus too hard on girls, just live your life and enjoy the experiences and relationships you build with all people; everything else will follow.

Travel, with a focus on the physically taxing things that are harder to do when you are older.

Invest what money you can, compound interest is real and it is the path to wealth (eventually).