What can I possibly do? How can I resolve this storage issue?

My Zte Phone Blade 452 has big storage issues.

First of all, recently my phone storage hasn't been able to load in the "Storage" section in "Settings", leaving it with the same message "calculating" the space I have. My SD Card is still able to calculate it's storage normally, whereas it hasn't been able to do so for my phone storage.

I do know however that I still have 1.34 GB left on my SD Card and that I have 177 MB left on my Phone storage.

However, although my phone says I still have space left as well as setting my SD Card as the default write disk, I regularly have to delete as many pictures and as much music possible due to my phone showing the message saying that my phone's storage is full.

Even more bizarrely, I can't re-download apps i had deleted to free space in the first place due to the reoccurring message of "storage full". This is weird since I have only just deleted the apps and should therefore clearly have enough space to re-download them again.

I already delete my cached data almost every day and am becoming increasingly desperate since it has come to a stage where some apps such as Instagram just crash every time I open them and my phone is becoming reduced to only containing a few apps.

I would really appreciate it if someone gave a bit of their time to perhaps help me out on this one.

Thanks in advance!