The relationship between users and courses and categories - laravel

Question

I want to be able to see, for example, only a certain group that is in that category among the courses that I offer on the site.
Anyone can not see the course of another group
In this way, when registering, users choose the category they are in and see the information about their group in their profile.
Should I use polymorphic?
User table
Course table
Classification table
And another table called categorizable which is polymorphic how many to how many?
please guide me
database
Schema::create('categories', function (Blueprint $table) {
$table->id();
$table->string('name');
$table->string('slug');
$table->integer('parent')->default(0);
$table->foreignId('category_id')->nullable()->constrained('categories')->onDelete('cascade');
$table->timestamps();
});
Schema::create('categorizables' , function(Blueprint $table) {
$table->unsignedBigInteger('category_id');
$table->unsignedBigInteger('categorizable_id');
$table->string('categorizable_type');
});
model category
public function courses()
{
return $this->morphedByMany(Course::class , 'categorizable');
}
public function users()
{
return $this->morphedByMany(User::class , 'categorizable');
}
model user and course
public function categories()
{
return $this->morphToMany(Category::class, 'categorizable');
}
form blade
<form class="g-3" method="POST" action="{{ route('register') }}">
#csrf
<div class="col-8 m-auto">
<input type="text" required class="form-control #error('name') is-invalid #enderror" id="name" name="name">
#error('name')
<span class="invalid-feedback" role="alert">
<strong>{{ $message }}</strong>
</span>
#enderror
</div>
<div class="col-8 m-auto">
<input type="text" required class="form-control #error('national_code') is-invalid #enderror" id="national_code" name="national_code">
#error('national_code')
<span class="invalid-feedback" role="alert">
<strong>{{ $message }}</strong>
</span>
#enderror
</div>
<div class="col-8 m-auto">
<select id="inputState" class="form-select" name="category_id">
<option selected class="d-none">select category</option>
#foreach(\App\Models\Category::all() as $category)
<option value="{{ $category->id }}">{{ $category->name }}</option>
#endforeach
</select>
</div>
<div class="col-8 m-auto">
<input type="password" required class="form-control #error('password') is-invalid #enderror" id="password" name="password">
#error('password')
<span class="invalid-feedback" role="alert">
<strong>{{ $message }}</strong>
</span>
#enderror
</div>
<div class="col-8 m-auto">
<input type="password" required class="form-control #error('password_confirmation') is-invalid #enderror" id="password_confirmation" name="password_confirmation">
#error('password_confirmation')
<span class="invalid-feedback" role="alert">
<strong>{{ $message }}</strong>
</span>
#enderror
</div>
<button type="submit">register</button>
</form>
controller
$data = $request->validate([
'name' => ['required', 'string', 'max:255'],
'password' => ['required', 'string', 'min:8', 'confirmed'],
'national_code' => ['required' , New Nationalcode],
// 'g-recaptcha-response' =>['required' , New Recaptcha],
'category_id' => 'required',
]);
// $user = User::create($data);
$user = User::create([
'name' => $data['name'],
'password' => Hash::make($data['password']),
'national_code' => $data['national_code'],
// 'category_id' => $data['category_id'],
]);
$user->categories()->sync($data['category_id']);