Put something in a hand

[K-Z]

Good day!

I am new to Gimp and already learned a lot from the forum, thanks for everything.
However i have 1 question.
I would like to photoshop something in a hand, a phone for example sometimes.
However, when I paste a new layer over the existing photo, the thing covers the whole hand. How do i get the fingers from the background to 'hold' the item in the hand? so that the hand is behind the item, but it looks like the fingers hold it.

thanks in advance!!! you are doing a great job all


I mean something like this:



But when i try it, the phone covers the whole hand, also the thumb that's covers it