Question regarding fetch

[Soroush]

I have finally managed to teach Lucy to go after the object I throw(Whatever it is), grab it, carry it and bring it towards me. However I have a problem teaching her to let go of the object when I ask for it.

It gets more complicated: When I have a treat in my hand and she knows it, she brings the object to my feet and drops it asking for the treat. This works for me, but I would love it if she actually kept the object in her mouth and put it in my hand when I ask for it.

I've tried the "Give me" command much more than the actual fetch itself, but it seems to not work.

Without treats, she doesn't give up the object and just carries it away. Once I turn around and don't give her attention, she let's go.

With treats, she lets go of it almost when she's at my feet and close to her treat, but she never gives it to me as in holding it near my hand.

What can I do to improve this?

Thanks in advance.