How can I change my training bonus

That's not possible.

The player has to be at your house for that

How can the training bonus be recovered if the club of the player in the field has no funds?

Ancelotti RMA: Comment peut procéder à récupérer la prime de formation si le club du joueur en pré n'a pas de fond

If the lending club doesn't have the funds, it doesn't change anything for you: you get your bonus back whenever you want. You won't be blocked, that's his problem. If he finds himself in deficit, it is because he has not managed his finances properly.

Blagoje Vidinic: Si le club prêteur n'a pas les fonds, ça ne change rien pour toi : tu récupères ta prime quand tu veux. Tu ne seras pas bloqué, c'est son problème. S'il se retrouve en déficit, c'est qu'il n'a pas géré correctement ses finances.

If the player is taken back and you have not yet recovered your bounty

Who is going to take the train bonus is it the owner or the person that take the player on loan