Advanced Eloquent ManyToMany Relationships

I have 4 tables:

Tournament

    id      |     name      
-----------------------------------
    1       |      National Tournament 2014   
-----------------------------------
    2       |      National Tournament 2015   
-----------------------------------
    3       |      Tournament Test   
-----------------------------------

Category

    id      |     name      
-----------------------------------
    1       |      Men >80kg   
-----------------------------------
    2       |      Women >80kg   
-----------------------------------
    3       |      Team Men >80kg   
-----------------------------------

Category_Tournament (List all categories available in a tournament)

id | category_id | tournament_id      
---------------------------
1  |    1       |       2   
---------------------------
2  |    2       |       2   
---------------------------
3  |    3       |       2   
---------------------------
4  |    4       |       2   
---------------------------

Category_Tournament_User (categories registered by user)

id |  category_tournament_id  |       user_id       
-----------------------------------------------
1  |              1           |        201 
-----------------------------------------------
2  |              3           |        202
-----------------------------------------------

I have 4 models ( Tournament, Category, CategoryTournament, CategoryTournamentUser)

I have no clue how to use eloquent relationship to link Tournament and Category_Tournament_User

I would like get the all the categories that has registered a user for a given tournament

Another example is to get all the users registered to a tournament.

In Model Tournament, I have

class Tournament extends Model{
public function competitors()
{

    return $this->belongsToMany('App\User', 'category_tournament', 'category_tournament_id', 'user_id' )
        ->withPivot('confirmed')
        ->withTimestamps();
}

I would like to get all competitors in a tournament.

It won't work, because it is relating tournament_id with category_tournament_id

I could do it in SQL, or in Model based queries, but what I can't understand is how to define and use ManyToMany Relationships between Tournament and Category_Tournament_User for example.

This is a key for such an elegant code, and I can't find the way to implement it, !

Please help me to find my way!!!

via Chebli Mohamed