Should I withdraw a submission? I worked on a paper in computer science (CS) from half a year approximately, so I decided to send it to the JUCS journal. They kindly informed me that they were not able to find enough reviewers for my article and so I decided to send it somewhere else. After that, I sent it to another journal that covers general topics in CS, but it got rejected. The justification was because they said the article lacked of the necessary algorithmic formalism but the problem is that only one reviewer sent out their comments after almost six months. I thought my paper was almost forgotten, because when I wrote to the editor I never got an answer.

After this rejection I submitted my work to a conference, and it finally got accepted. The recommendations were to proofread the paper, and well just to add more references. I consider that is valuable to mention that the journals and this conference are indexed in Scopus.

The problem that I have is that I found that there is a top ACM conference in this field. So, I do not know if I should withdraw my paper from the conference that already accepted it and re-submit it for this new conference. The reason for doing this is because I am very curious about what would be the feedback of the reviewers in this conference. I know that maybe it will get rejected, because I saw that the submissions come mostly from well renowned universities such as MIT or Stanford.

Bottom line, what should I do in this situation? Any advice? Should I just present my research into the conference that already accepted it, and after that to send it for comments to a professor in this area?

Thanks
This is clearly a judgement call and I can only offer opinion. But if you withdraw from the conference at which it was accepted you won't be able to resubmit there if you are rejected by the other. This narrows your future options for this paper. 

I'd therefore suggest that you stay with what you have (a bird in the hand is worth two in the bush). 

But this is just one paper. Write more papers and expand your knowledge about good places to submit them. One paper is just one paper. It isn't your entire career.