How do I become a successful topline writer?

Hey you all! It's me again! I wanted to post this video up because for the past year and a half now, I've been wanting to get more into topline writing (a singer or rapper comes up with the melody & lyrics). My strengths are usually with track writing (coming up with the instrumental/beat). But for anybody who happens to be in the industry that can help me with some constructive suggestions, I welcome them all! Because of the area that I currently live in, I do not have the access to people to collaborate with. So by sheer necessity, I have to learn how to do all of this by myself.

I've taken at least a semester of classical voice training in college (but my professor discouraged me from singing anymore when I asked her for a recommendation for Berklee College of Music, she in so few words said that I wasn't so good because I'd only studied with her for 6 months (and she's a classical singer). I used to love to sing, but I pretty much stopped after that moment 8 years ago.

I try to work on lyricism whenever I can. I work on my wordplay, poetic devices such as assonance, internal rhyme, similes & metaphors. I also try and work on rhyme scheme, flow, breath control, and cadence.

One person that I really look up to that's a topline writer is Drake. He's my favorite rapper and singer (he reminds me a lot of Craig David). I wanna be able to topline write just like him. Here's my video about everything I'm talking about and a couple of songs of his that are examples (one sung, one rapped):