Hello student, yes ofcourse you can score 500 plus Mark's in neet 2020. Scoring that mark is not that difficult. And you have specified that you have previous knowledge, then it is not that difficult to score.

Here are few tips

1. First, have all the concepts in ncert text books well known. Every book and corner of text books

2. Take frequent mock tests on whole. As many as possible

3. Know the weightage of the chapters in each subject and then prepare, practice mocks tests accordingly from online or while solving papers or topic wise bits know the weightage and solve them accordingly

Here is the link for weightage

https://medicine.careers360.com/articles/neet-chapter-wise-weightage-and-important-topics/amp