Install some useful fonts, in order to improve the compatibility with documents from Microsoft Office. Namely a package containing some old Microsoft fonts and two modern Google-made free replacement fonts.
I. First the package with old Microsoft fonts:
a. Launch a terminal window
b. Transfer this line into the terminal:
Code:
wget http://ftp.us.debian.org/debian/pool/contrib/m/msttcorefonts/ttf-mscorefonts-installer_3.8_all.deb -P ~/Downloads
Press Enter. With this command, you download the installer package from Debian, the Debian package is cleaner
c. For the actual installation, transfer this line into the terminal
Code:
sudo apt install ~/Downloads/ttf-mscorefonts-installer_3.8_all.deb
Press Enter. Type your password when prompted. Press Enter again.
d. Now you will be confronted by a license agreement from Microsoft.

If so, hit the Tab key to activate <Ok> (which then turns red), and press Enter.
e. In the next window you'll be given the chance to say Yes to the agreement: hit the Tab key to activate <Yes> (which then turns red) and press Enter.
f. Finally, copy/paste this command into the terminal:
Code:
sudo dpkg-reconfigure fontconfig
Press Enter.
II. Now install the Google-made free fonts Carlito (replacement for Microsoft's modern proprietary Calibri) and Caladea (replacement for Microsoft's modern proprietary Cambria). Like this:
a. Launch a terminal window
Transfer this line into the terminal:
Code:
sudo apt-get install fonts-crosextra-carlito fonts-crosextra-caladea
Press Enter. Type your password when prompted. Press Enter again.
b. Now you're going to configure Libre Office to use them as replacement for the Calibri en Cambria fonts from Microsoft:
Launch LibreOffice Writer.
In the panel of LibreOffice Writer: Tools - Options... - section LibreOffice: Fonts
Tick: Apply replacement table
c. Type in for Font (it's not in the dropdown list, you have to type it): Calibri
Replace by: Carlito (it's in the dropdown list)
Press the button with the green tick.
Tick: Always and Screen only
d. Now type in for Font (it's not in the dropdown list, you have to type it): Cambria
Replace by: Caladea (it's in the dropdown list)
Press the button with the green tick.
Tick: Always and Screen only
Click the OK button.