I have been through the 30 lessons with Camille.

These lessons were very interesting, but I cannot see how I can improve my voice just with those lessons which last about 5 to 8 minutes each.

The lessons were basic, very well taught by Camille (excellent English accent, intonation etc.), but what do I need to do next, after the 30 lessons?

Hi, Ananda! The hope is that now you have a foundation to work from moving forward. Continue with a daily warmup (there's a large variety on the site), work on songs you love, and check out the other lesson series to keep learning and building your skills! I recommend the level 2 beginner course as a next step.