Bonjour ! Lorsque, sur mon logiciel Audacity, je change un fichier WMA en fichier mp3, celui-ci ne dure plus q’une demi-seconde, autant dire à peu près rien pour une chanson. 
Est-ce que quelqu’un peut m’aider ?
Hello ! When I translate a song in WMa to a song in MP3 on my computer, then my song lasts less than a half-second ! Could someone help me ? 
You need to add FFmpeg to your computer to import the WMA into Audacity
http://manual.audacityteam.org/man/FAQ:Installation_and_Plug-Ins/fr#Comment_puis-je_t.C3.A9l.C3.A9charger_et_installer_la_biblioth.C3.A8que_d.27import.2Fexport_FFmpeg_.3F
and you need to add LAME to your computer to export the MP3 from Audacity:
http://manual.audacityteam.org/man/FAQ:Installation_and_Plug-Ins/fr#Comment_puis-je_t.C3.A9l.C3.A9charger_et_installer_l.27encodeur_MP3_LAME_.3F .
If you already have those libraries then you are not selecting the correct audio to export.
Make sure you have Audacity 2.0.3 from here:
http://audacityteam.org/download/ .
Gale