I have 32 GB external, but my internal is only 4GB! My mom bought me a phone. It's Samsung Galaxy J1. And It says that it has only 4GB in my internal storage. But I have 32 GB external storage. 

So, I downloaded all apps that I wanted then I  moved it all (that can moved)to the external storage. 

But when I tried to download a new app, it says that my internal storage is full! And now, I can't download some apps nor pictures and music. 

Yes, I do have a lot of space left in my external memory. But it looks like nothing because it's useless now.

So please, help me from my problem. And w/o rooting my phone. Thanks in advance.
From my point of view, the best solution is to root Your phone and install Links2SD or App2SD ROOT PRO form Play Store. If rooting is not avaliable (lost of guarantee) please use App2SD for non-root users. There is a lot of such apps in Play Store. It moves parts of apps to SD card and frees space in internal memory.
But if You root Your device, all app parts can be moved to SD, even part of system apps.