The phone has 16GB of storage to start with, before anything is loaded onto it. Then you have recovery and the whole system loaded. Plus a few other partitions.
To see how storage is actually set up, connect the phone to a PC (that already has the
Huawei driver installed), install
ADB and Fastboot Tool, open a cmd window and type:
adb devices
When you see your phone listed (it will be the phone's serial number), type:
adb shell df
(You could also issue the
df command from a terminal app, if you have one installed, but you probably don't have enough space to install one if you don't already have one installed.)
Look for a line that says
storage/emulated (on the right), or something like that. It's usually the last line. (It may also say
sdcard.) Look in the 2nd column - that's the total amount of space allocated to internal storage. The rest is being used by the phone. (The 3rd column, Used, includes all the system apps. The 4th column, Available, is all you have left - which is probably almost nothing.)
In late 2019, a "small" phone is 64GB total storage (not the 16GB your phone has). 128GB gives you some breathing room. That's why phones with 512GB of storage are currently being sold.