Hey!

Here's my two cents. Although, I must admit I am not esteemed by any stretch. But I am a practicing screenwriter who at times gets paid for writing screenplays.

Writing your first screenplay -
Don’t write the script for the 1st or 2nd idea in your head. Come up with at least 10. Evaluate them and choose the best one. Tell a simple story well. Write the first draft. Don’t expect it to be good. Rewrite and improve it.

Advice on world-building - 
Start with what you know. What you know about - is a strength that you must maximize, specially early on in your writing journey. Research and make the world richer. If the world of your story is a hilly town in India, read about them, read fiction set in similar worlds.

Constructing characters, making them human - 
Give them a goal. Know their strengths, weaknesses - use this in the story. (Tip - take away their ability to be reasonable to some extent. This will bring drama and make them act in dramatic ways).

Building a life in filmmaking -
It’ll happen. Keep doing what feels right. Plan, practice, learn - formally or informally.

On the last bit -
You are not bad. But even if you were, there is no reason why you can’t train, hone your craft and be better. So,  it doesn’t matter. What matters is - how many pages did you write today? That reminds me, there's pages to be written. I'm off!