With your current domain model structure. You can accomplish this with a datagrid for projects, a dataview set to listen to the projects datagrid, and then another datagrid for answers with an xpath constraint.
This is the domain model I used.
This is the page I created.
The left side is a datagrid of all the projects. The right side is a datagrid inside a dataview. The datasource of the dataview is set to "list to widget" and I selected the datagrid of projects. The datagrid of answers is showing a column of an attribute from the answer table and then another column of an attribute from the questions table.
The xpath constraint for the answers datagrid is
[Module.Answer_Project/Module.Project = '[%CurrentObject%]']
This constraint ensures when a project record is selected, the grid of answers/questions only shows that specific projects Questions/answers.
Here is some helpful documentation:
listen to widget datasource for dataviews
Hope this helps!