Issues with the font

Hi everyone,

I have a really annoying problem : when I write something (anything) and then press “Enter”, my font changes and is automatically replaced with Liberation Serif… (I want to stick to Calibri).
I changed the parameters to set Calibri as my default font and when I open a new document, write on it, it uses Calibri, but if I press enter… it changes.
I did this : How do I set the Default font to Times New Roman size 12?
It works, except if I press enter. (I don’t feel like I am clear, at all)

please, this makes me completely mad… Help me…

Thanks