Is it permissible for the trustee to dispose of money entrusted to him for investment, and then continue to send the profits from his own money to the depositor, and what should he do if he wants to rectify the matter?

We understand from the question that the person in charge took money from his employer to invest it in a project with his employer's permission, and there is no harm in that. However, his withdrawal of the money from the project and his disposing of it without the owner's permission is an encroachment for which he is liable, and he must return it to its owner. The amount he paid to the owner of the money as profit is not rightfully his, because his money was taken by way of encroachment and was not invested. If the encroacher had invested it and profited from it, some scholars are of the opinion that the profit belongs to the encroaching investor, while others believe it belongs to the owner of the money. If the questioner paid those amounts as a donation, then there is no harm for the owner of the money in accepting them.