Removing the shelf
The previous van owner was an electrician and built some kind of shelf that surely suited his needs but not ours, so we removed it. We also wanted to start from scratch. Thanks to Jakob for helping out in this.
After removing the shelf we found out that the previous owner drilled a few screws through the floor of the van (on peut parler de "vis cachées"), and - more concerning - a large hole adjancent to a structural piece, previously holding a pipe.