Show amount and duration in graph

[Wilco()]

I need to report on the amount of priority 1 IT tickets in a month.

Sample is attached of how the data looks like.

I need to build a table per month with the amount of open tickets per month. The ones closed should not count.

From this I want to use this data to show a graph, per month with the total open tickets.

How do I do this?

 

[vletm]

Wilco()
Did You upload a correct file?
Now, there are 'just' Ticket Number, Date opened and Date closed!
Something is missing or how?