I found out how to fix it, the sculpting that is, gods knows what happened to the legs, as it happens the model is unable to sculpt because it has a to low number of polygons, which as it happens when you smooth it, it will try to smooth all the polygons together like normal, but the problem is, that the polygons are so big that when blender tries to smooth them, it just ends up smoothing very aggressively, and so the model is eaten, in other words, the bigger the polygon, the more aggressive the smoothing will be.
so to fix this I pressed TAB, while in sculpting mode, and added in the add section "subdivide", which made the model have a lot more polygons, which made most of the mesh more intricate, and the polygons much smaller, which made them possible to work with.
then all you need to do is to use the clay brush, and sculpt normally, putting clay on the model, and smoothing it later, which since the polygons are much smaller, the smoothing will be much more gentle.
it should also be noted that I am using a sculpting addon for blender, so I don't know if the subdivide option is there in the vanilla one, so I am linking the addon just in case.
new dinosaur :3 https://imgur.com/a/QRWRr