Render blocking can be a huge issue, especially for users with low-end equipment or a slow internet connection who are trying to view your website. As I have studied Javascript, HTML, and CSS for 4+ years, I am quite familiar with procedures used to unblock rendering, such as media queries, code placement, etc. Completion time for this project varies based on how large and complex your website is. A website with one page can be completed in less than a day, while large, multi-page websites with complex scripts may require 3-4+ days. Price is also flexible.
Have a wonderful day,
Andrew G.