applications - KitKat - How to identify the REAL size of apps (app + datas + ...) to be able to install other ones

I had an iPhone for 4 years and I now have a Samsung Galaxy S5 running KitKat 4.4.2.
I've started the migration from the one to the other downloading my prefered apps.
I've just downloaded 40 little standard apps, half of the work, and my S5 already tells me that it cannot donwload any more apps from the Playstore, not enough space on the phone. What ??? But... I still have gigs of space... and I already moved out all possible apps from internal memory.

I've seen that I could bypass this by rooting the phone, but I can't deal with that. That's not a solution.

So I've started to search which are tha apps that take the more space.

On the iPhone, when I wanted to know the exact size that an app, I could see this onto the settings or into iTunes, giving the size of the app + its datas.

On KitKat, I don't see this information anywhere. As an example, I have "Maps with Me" installed, from which I have donwloaded around 1 gig of maps. It should be the one and largest app I have. But the best I can see about its space see is into the Application settings panel the following informations :

Total : 60,41 Mo
Application : 5,11 Mo
Stock on phone app : 55,09 Mo
Datas : 116 Ko
Stock on phone datas : 96,00 Ko
Cache : 64,00 Ko

Where are my gig of maps ? How can I sort my apps by their real space usage ?
And more, how can I install more than 40 littles apps on such a phone ? That seems incredible... There must be a standard way of doing that ?

EDIT 1

Clean Master tells me that "Maps With Me" is 656 Mb large. Well, OK, but isn't the default marvelous system able to do that ? Because I don't want such apps on my phone, just to do what the basic OS should do and bore me with other functionalities I don't want.

Clean Master also tells me that I have 64 apps occupying 2,5 Gb.
And that My free system space is 120,32 Mb.
After a clean with this app...
I only have my phone since 1 week, and I've nearly done nothing yet with it.

FYI, I've made a factory reset at the first use, and deleted any possible unwanted apps.