Moving sdcard to ExtSdCard

I was an Android beginner, I know nothing of 'hacking' some Android stuff. I found several issues of this case but no one that I look pretty ideal for my case. My Samsung Galaxy Ace 2 has been inserted a new SD Card after a several time using no SD Card. That makes the system create sdcard in it's internal storage. Then my storage information (Setting -> Storage) become 3 parts, which: **Device memory** (internal), **USB Storage** (internal), and **SD Card** (extSdCard). This thing become very annoying since my internal wasn't so big. And when I open my **Gallery** it pop some notice There is not enough space (0 MB) in your device memory. Delete some files. And always redirect me to the **Files**. On my **Files** there is 2 folders, which: **extSdCard** and **sdcard0**. On the setting of Files. I **can't** change the Set home directory that refers to /storage/sdcard0 to (my hope) /storage/extSdCard. I done trying to moving all apps to internal storage with hoping that **USB Storage** not full, but it doesn't give any good solution just yet. I read several post and forum, also several solution using adb but I don't think those solution can manage all problem, since because of this case, I can't save any voice note or picture from social chatting apps, in some case, I can't receive any bluetooth transfer also. So I want that **USB Storage** begone, and my sdcard0 was symlinked to the real external SD Card, or another step that make my system become like the old like Android system. Please help me. Thanks a lot before. FYI: right now, my phone isn't rooted yet. But I can root it anytime, if it really needed.