Query Report:To Retrieve Data from A/R Invoice and A/P Invoice

Hii Experts,

I am a new Sap B1 Trainee.I am facing a problem when retrieving data from A/R Invoice and A/P Invoice in order to track

Expenditure and Revenue according to a Bussiness partner,

I am using union to retrieve the information,but it is saying a error that Error Converting Varchar to Numeric and also

i would like to know how can i show the total final payment by reflecting Downpayments in A/R Invoice and A/P Invoice

With Regards

Cherry.