Hello,

Is it multiple axis or multiple series ?

If it's multiple series then try to create two series accordingly and pass the same values for the X axis on both series. 

Hope it helps!

I want to create combine chart (bar + line) like this :

You should be able to do that by changing some settings in the chart/series. I would recommend you take a look at the documentation section https://docs.mendix.com/appstore/widgets/charts/

there is an example like yours here