function onEdit(e) {

var sheet = e.source.getActiveSheet();
if (e.range.getA1Notation() !== 'C3' || sheet.getName() !== 'Overview') return;
switch (e.value) {
case 'All':
    sheet.showColumns(1, sheet.getMaxColumns()-1)
    break;
case 'January':
    sheet.showColumns(1, 2, 3, 4, 5, 26, 27)
    sheet.hideColumns(6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24)
    break;
case 'February':
    sheet.showColumns(1, 2, 3, 4, 5, 6, 7)
    sheet.hideColumns(8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27)
    break;
}
}