Hi Leondro,
this is probably because you show the same list of data activities in every activity item. What you probably need to do is change the data source from Database to Over association. That way you can show all data activities that are linked to that specific activity.
It is important that when creating those data activities you set an association between activity and data activity, otherwise those lists will remain empty.
From that moment on, Mendix only shows the data activities that are linked to your activity.
I hope it works!