Ils nous manque quel'que truc la dedans (jabber, mail)

Just force overwrites on the installation of the conflictive package:

sudo dpkg --force-overwrite -i /var/cache/apt/archives/libqt5multimediaquick-p5_5.0.1-0ubuntu1_i386.deb

If that's not enough for the installation to succeed, you can also force everything dpkg can complain about (be careful doing this!):

sudo dpkg --force-all -i /var/cache/apt/archives/libqt5multimediaquick-p5_5.0.1-0ubuntu1_i386.deb

After doing that, just issue the suggested command again:

sudo apt-get -f install

Automatic selling / buying stock algorithm