data reduction

I have a text file that I need to reduce by deleting rows of data.

I get the data file which I am able to open just like I would a .csv file.

Each of these files contains the results for 5 parts on average, the sample below only has 2.

I need to reduce the rows of data per part by keeping only every fifth row of data.

I have attatched a sample of the file I need to reduce