1. I would not do the same things second time around, wouldn't be doing full time university and full time work, I would quit the university, do full time not for 5 years as I did but for maybe 4, move onto the contracts then as I did at first, but not do contracts for 10, instead do it for 5 and start my own business 6 years sooner after getting just enough experience anyway.
2. I wouldn't bother buying and fixing and renting/selling properties as I did on the side, that diluted my effort and pulled me back from starting my own real business.
Basically if I could talk to myself 20 years ago, I would tell myself to skip college altogether, work right away (as I basically did anyway, but I did full time studies and full time job, which was unnecessarily difficult). I would make sure to explain to myself how to properly save money from much younger age and tell myself to start the business much earlier.