You need to organize your repeater entries into rows, with that done you can call update_field() using the array. Here’s an example of what you need to use as the value for update field when dealing with a repeater
array(
// each row of the repeater is a nested array
array(
// each element of the row array is a subfield value
'field_123456' => 'field 1 value',
'field_234567' => 'field 2 value',
), // end of first row
array(
// each element of the row array is a subfield value
'field_123456' => 'field 1 value',
'field_234567' => 'field 2 value',
), // end of second row
) // end of repeater
Let me know if that helps at all
