The webservicedatatwindow is not retriving any data and retun -1
This could mean that the datawindow object never got set on the datastore you are using to host it, potentially because the datawindow object is missing from the compiled program. You'll need to do so debugging. Check the return code from SetTransObject, trace the database connection, etc.
Should we have to pass only string variables as input while creating a webservice in powerbuilder 12.5.1.
No. Try using Fiddler to monitor the call that PowerBuilder is making to see what it's request looks like. Compare that with a working call using SOAPUI.