implements of the OOP concepts in Laravel

 Hello everyone, I hope you are healthy. Usually, I've confused about how to follow OOP rules as using Laravel! for example how to follow SOLID rules with the framework.

For example, I want to build a simple marketplace for a company and I follow this method.
For example for the invoicement part :
1- First, I created an interface for it.
Code:
InvoiceIf.php->
<?php
namespace App\Classes\Interfaces;
interface InvoiceIf
{
public function customer();
public function sellerUsers();
public function products();
public function prices();
}

Then, I've created a Eloquent Model like:
Invoice.php
<?php
namespace App\Classes;
use Illuminate\Database\Eloquent\Model;
use App\Classes\SellerUser;
class Invoice extends Model implements InvoiceIf
{
final public function customer()
{
return $this->hasOne(Customer::class);
}
final public function sellerUsers()
{
return $this->hasMany(SellerUser::class);
}
final public function products()
{
return $this->hasMany(Product::class);
}
final public function prices()
{
return $this->hasMany(Price::class);
}

}
Third, I create a Controller to handle user requirements.
but in this time, this method that I've followed it is true or not?
please help me...