The meat of the deal is that voters in the six faciliteitengemeenten / communes à facilités will get to choose between Flemish and Francophone lists of candidates for the European elections, and between Brussels and Flemish Brabant constituency lists of candidates for Chamber elections, and this will be anchored in the constitution. (Up to now, everyone in the whole of BHV got to choose from both lists for the European elections, so this will now be restricted to Brussels and the six gemeenten; and there was no Flemish Brabant constituency for the Chamber, the west of the province being bundled with Brussels to make BHV and us in the east having our own Leuven constituency.)
Clearly it was too difficult to decide how the direct elections for the Senate could be fitted into this, and the simplest solution was just to stop having them. The Senate will continue to exist - the 21 Senators currently chosen by the Flemish, Francophone and German-speaking community parliaments will be increased to 51, and the 10 co-opted Senators remain. But the overall number thus drops from 71 to 61, plus the King's three children who are members but not usually counted.
So, at a moment when crazy plans to introduce directly elected members of the UK's House of Lords are being discussed, Belgium is going the other way... Edited to add - I had missed the crucial point that the royals are to be kicked out. So Belgium is removing both directly elected members and hereditaries from its upper house.