its possible change the downloading directory for the marketplace content?
It’s not directly possible to do that. Take a look at this thread -> https://forums.unrealengine/showthread.php?65444-How-change-marketplace-asset-downloading-directory 
"“Sample projects are now downloaded into your Vault, which is located within the engine install directory. From the vault files, you are then able to make a copy of the project where you wish.”
"1) Junction the vault files to your storage drive, (windows thinks they are in the default directory (C:\Program Files\Epic Games\Launcher\VaultCache) but you can have them actually on your HDD)
2) Or you could uninstall and then reinstall the Unreal Engine on to your HDD (but then the Engine would not take advantage of the speed of the SSD)
3) Wait for Epic to realise that most of us are in a transition between HDD and SSD’s needing both for adequate speed and storage, and that an option for Vault location on install would be a good idea… "
oh thanks! and oh! i ask this question before :o i forget about that.