Delete text and re-creating text

#1

I created text and lines upto 100 but I want to show that line only 50. Another 50 lines I want to hide. How can I do that?

how can I delete that line and text and recreate with increaing number 5.

For example: first 5 lines come to 0,5,10,15,20. then i will scroll down that line the number will change to 5,10,15,20,25. this will happen until 100.

How can I do this thing?