How to properly structure a model in MVC on PHP? Problems with Fat Model and business logic

Hello everyone! I'm a beginner PHP developer and have been writing in Laravel for several months. But I feel like I'm doing something wrong with models.

I have an online store project. Initially, I put all the logic into Eloquent models. For example, my Order model contains:

class Order extends Model
{
    public function calculateTotalWithDiscount($couponCode) { ... }
    public function validateStock() { ... }
    public function sendConfirmationEmail() { ... }
    public function generateInvoicePdf() { ... }
    public function applyLoyaltyPoints($userId) { ... }
    public function checkFraud() { ... }
}

Now this model has over 2000 lines. I understand this is a "Fat Model", but I don't know how to properly separate it.