Hi Bequimão, thanks for your reply.
I will try your tip about language configuration in textual console.
No new install is needed.
I am planning to install also Siduction with Razor-qt, in order to test the D.E. Razor-qt, in a partition next to the one which contains Siduction with KDE.
May be also for Siduction with Razor-qt is better to update sidu-installer before installing.