Teach Me

How to send a another menu to a existing main menu and add a back button or back item to go to main menu using gui?

Like
$inv->setItem(0,Item::get(339, 0, 1)->setCustomName("Next Page")->setLore(["§r§7---"]));;
$player = send($menu);
if($item->getId() == Item:APER and $item->getDamage() === 0){
$sender->getLevel()->addSound(new PopSound($sender));

Sorry for bad code!! Im Newbie

 

you need to send full code. i cannot solve that in this size