Omg, such a nice decision, thx for comments it helped me to understand how it works!)

Your code not working is not a kata issue. Read the documentation: https://docs.codewars.com/training/troubleshooting/

Why my code doesnt work properly? I did as described in tasks, but it doesnt work.

ItemIndex 22
ItemsArray [ 1,
  2,
  3,
  4,
  5,
  6,
  7,
  8,
  9,
  10,
  11,
  12,
  13,
  14,
  15,
  16,
  17,
  18,
  19,
  20,
  21,
  22,
  23,
  24 ]
PageArray [ [ 1, 2, 3, 4, 5, 6, 7, 8, 9, 10 ],
  [ 11, 12, 13, 14, 15, 16, 17, 18, 19, 20 ],
  [ 21, 22, 23, 24 ] ]
SearchedItem 23
ItemsPerPage 10
ItemArray [ 21, 22, 23, 24 ]
Index 2
pageIndex returned incorrect value

jesus, so cool, hoped one day i will be coding like this.