@faridalabib If it’s just 50 articles then you are likely better off doing the split by hand. Doing it by hand should take less time than it would take to figure out how to script splitting a file into 50 parts, debugging it, etc.
One hint is to number your 50 files from 01, 02, 03, … 49, 50 using leading zeroes for 1 to 9. Then it will be easy to reassemble the 50 files into one large file again to verify that it’s the same as the original large file containing 50 articles.