Can you illustrate or mockup what you are expecting as results? I'm not understanding from the text and viewing the workbook. What is it you'd like to have happen in the visualization, and how will the user interact? I'm not sure what you mean by "multil filter and also show all dates at the same time". Do you mean in the viz, or in the filter?
Of course, filtering on a date will always remove data from the visualization, so if you are hoping to choose a Month but still see all dates, a Filter will not get you there.
If you'd like to give another shot at describing the problem, someone will gladly help if there is a solution that can be applied. Happy analyzing!