Thank you Trent,
I finally found this page yesterday : https://support.google.com/chromeboo..._topic=2589149
And I understand that SKYPE cannot be installed on my Chromebook. The equivalent is Hangouts. Thing is my friend in Panama doesn t have Hangouts on his smartphone, and old Samsung Ace II x. And my own smartphone is even older, and blacks out often when I use wifi. I m disappointed to see that there is no compatibility between 2 Samsung products, my Chromebook and my friend's Ace II.
So I will buy a new phone, who will support Skype and Viber. But I find the new models so big =^(