I need to get that by using the for each function

1. Here's the approach I would take (to help you work it out for yourself):Treat each array as a single item in a new array (that is, your new array is a "list of lists")
2. iterate over that new array using a!forEach()
3. for each item in the array use the function that tells you how many items are in an array

An alternative approach is to use the merge() function to generate a "list of lists" and use the length() function (which ignores null values in its counts):

a!localVariables(
  local!myArray: fn!merge(
    /*{ 1, 2, 3, 8, 9, 9, 9, 9, 9, 80, 90, 70 },*/
    /*{ 56, 76, 54, 32 },*/
    /*{ 20, 23, 45, 54, 32, 54 },*/
    /*{ 1, 2, 3, 4, 5, 6, 7 },*/
    /*{ 11, 12, 13, 14, 15, 16, 17, 18 }*/
    { 1, 56, 20, 1, 11 },
    { 2, 76, 23, 2, 12 },
    { 3, 54, 45, 4, 14 },
    { 8, 32, 54, 4, 14 },
    { 9, null, 32, 5, 15 },
    { 9, null, 54, 6, 16 },
    { 9, null, null, 7, 17 },
    { 9, null, null, null, 18 },
    { 9, null, null, null, null },
    { 80, null, null, null, null },
    { 90, null, null, null, null },
    { 70, null, null, null, null }
  ),
  a!forEach(
    items: local!myArray,
    expression: fn!length(fv!item)
  )
)

An alternative approach is to use the merge() function to generate a "list of lists" and use the length() function (which ignores null values in its counts):

a!localVariables(
  local!myArray: fn!merge(
    /*{ 1, 2, 3, 8, 9, 9, 9, 9, 9, 80, 90, 70 },*/
    /*{ 56, 76, 54, 32 },*/
    /*{ 20, 23, 45, 54, 32, 54 },*/
    /*{ 1, 2, 3, 4, 5, 6, 7 },*/
    /*{ 11, 12, 13, 14, 15, 16, 17, 18 }*/
    { 1, 56, 20, 1, 11 },
    { 2, 76, 23, 2, 12 },
    { 3, 54, 45, 4, 14 },
    { 8, 32, 54, 4, 14 },
    { 9, null, 32, 5, 15 },
    { 9, null, 54, 6, 16 },
    { 9, null, null, 7, 17 },
    { 9, null, null, null, 18 },
    { 9, null, null, null, null },
    { 80, null, null, null, null },
    { 90, null, null, null, null },
    { 70, null, null, null, null }
  ),
  a!forEach(
    items: local!myArray,
    expression: fn!length(fv!item)
  )
)