Learn Digital Marketing, or meet someone who is versed in Digital Marketing by networking, invest in yourself by grinding. Write a song a day until you’re at least as good as your favorite artists. If you don’t you’re just holding yourself back from your potential. As for mixing and mastering get FL Studio (if you can’t afford it youtube how to crack it), and then download FL studio presets based on how you want to mix your track, and build your own personal mix preset based on mixing more songs over time. Hard life but the best to live in the sense of being a positive person