You can't export all graphs at once, but you can export individual data points from the Reports function of Pipedrive's Progress tab..
To export specific data points from Reports into an excel file, go to Progress > Reports and click on any bar, point on a graph, or number in any graph you would like to export.
That'll give you a popup showing the list of all of the data included in that number or point on the graph.
In that popup, click the ... button and select Export statistics results.
Choose which file type — between .csv and .xls — you would like to export these statistical reports into, and you're done!