What would you learn if you had to start all over again

Hey everyone I just joined Indiehackers and I'm super happy I discovered this AWESOME community.

My question to you is: if you had to start all over again, what (technical/design skills/programs) would you focus on learning?

I started 6 businesses in the past but realized that I really want to take a more indie-approach to business which made me realize I need to seriously improve my skills both coding and design related.

But where do I start? I'm thinking of doing some courses on Codeacademy amongst others. Apologies for the noob question in advance.

PS: THANK YOU for sharing all your knowledge and insights!