Thankyou so much and congratulations to you as well.

About quality content, personally I think there are a few things that contribute in improving the quality.

1- First impression of the post should be good. It should look visually appealing. That can be done by taking care of text and image alignment. Proper use of markdown.

2- A post should be readable. I think one should write in whatever language he/she is comfortable with but grammar and spellings should always be correct and punctuations should be used where necessary. These things make posts readable. There a lot of tools for checking for that like spell check and grammarly.

3- A post should consist of reasonable amount of words. Not too short and not too long that reader gets bored.

4- Avoid plagiarism at any cost and give proper citations.

Other things like good vocabulary, writing style and creativity comes with time. These are secondary things which contribute in quality and develop with consistency in writing.

Tip: Reading books or stuff helps you write better.

Hope you find that helpful.