Power BI Report Builder- Report having multiple sheets

Ok, say you have a data like

and would like to show sum(QtyKg) for each Company in separate pages/sheets

First, add a matrix and design it how you like it.

right click over "CompanyKey" group under "Rows groups" and select "Group properties" and then "Page breaks" tab and click "Between each instance of a group"

By doing this, your report shows your report as an each group on separate pages. And if you export to excel, on separate sheets. 

But, for excel there is still a problem. sheet names are default to Sheet1, Sheet2.... and son on. To rename those sheets; click on to select "CompanyKey" group under "Rows groups" and then at the right you will see "Properties" pane. Drill to "Group -> Group -> Page Name" property and open expression combo box, then set what ever you want for the expression which will be shown as "Sheet names" in excel.