YEAAHH!! I did it! I just made a transfer of a .band folder from my PC to my iPhone through iExplorer!
This was my steps
1. Download iExplorer and install it. Connect your iPhone
2. Find the folder "com.apple.mobilegarageband" in iExplorers browser
3. Drag and drop your folder .band to the folder "Documents". (!! Your'e not done yet!)
4. In GarageBand on your iPhone press the plus-button as you would start a new song. Choose "Copy from iTunes". Choose your imported song.
5. Start rockin'
I've searched 5 hours to find this solution and man am I glad to finally have my songs back!! 😁