Help! Sales progress funnel chart

Hi,

I'm trying to run a funnel chart to measure the progress of opportunities through the sales pipeline. I'm sure its glaringly obvious, but I can't seem to

a) create a timeframe (I know there's a slicer but it doesn't seem to work) in order to see progress over certain periods

and b) pulling the right information so that I can see how many opportunities are at each stage. Ideally I'd like the funnel layers to be 10% at the top-100% at the bottom with the number of each opportunity that's sitting at that stage. So that I can slide the time along and compare how many opportunities made it all the way through to close.

Sorry for the garbled explanation, but if anyone can help it would be really appreciated!

G.