When Didier Masela left the band was it before or after the release of Solola Bien (after their flop at Stade Des Martyrs) ?

After Palais des Sports. He didn't return with them and came some weeks later to form his own band.

Did he left because of a strong argument he had with Werra. I heard that Werra said very bad things to him.

I've never seen Madeleine so crowded. This and Papa Wemba's tour of 2000 were the last tours in the Schengen who started in Brussels. Because before that all Congolese artists were starting their tour in Brussels (except Koffi Olomide)