First time! Thank you so much for your time

I'm looking to evaluate the effectiveness of our social media posts. The metrics, and columns, are Impressions, Reactions, Comments and Shares. Each row has data on each of these, and I'm hoping to find the percentile of each of these numbers and then the average of those percentiles.

For example
Impressions: 5000. These 5000 impressions are in the 45th percentile compared to previous posts.
Reactions:150. These 150 reactions are in the 40th percentile compared to previous posts.
Comments: 20. These 20 comments are in the 60th percentile compared to previous posts.
Shares:10. These ten shares are in the 50th percentile compared to previous posts.

I would like a cell that combines this data to display one percentile, which in this case would be 48.75; therefore performing slightly under average compared to other social media posts.

I can't work out how to do it! Here's a link to the spreadsheet: docs. google. com/spreadsheets/d/1upP38dVJ6W7S78XiHcJaDYf043bg3_dHZQCGSd654pM/edit?usp=sharing