Answer 1

1. Don't allow your TODOs to pile up.
2. Write tests. And if you do not, make sure your code is easily testable. (Tip: seperation of concerns and fewer impure functions)
3. Always spare time for practicing new concepts(especially if you code professionally)
4. Don't deprive yourself of sleep. Less time means more productivity.
5. Learning to read code will improve the way you write code.
6. Never idolize a programming language. Use what is best for the job and remember that everything dies eventually.
7. Learn about version control.

Answer 2

One tip is to adhere to the SOLID principles: https://scotch.io/bar-talk/s-o-l-i-d-the-first-five-principles-of-object-oriented-design
Write unit tests... consider a TDD approach: https://www.guru99.com/test-driven-development.html
Refactor code you write to make it better and improve your understanding of it.
Add comments to code to help yourself and others in the future understand what it does.

Answer 3

Consistent practice would be my first bet

Answer 4

You should do competitive programming or participate in contest to improve your programming skills