HI vijayalakshmi Kurra,
You can add your Form widgets manualy and select the appropriate Attributes or if you want the form widgets to be filled automaticly by mendix. Delete the DataView in the TrainingEvent_NewEdit if already present. Now drag a deatview and select the conetect object, after selecting the context entity you will be asked whether mendix can prefill the form widgets with the attrbutes , you can click yes in the confirmation pop up, later you can delete the other form widgets which are not necessary.
Hope this helps.
It may caused whether you taken an attribute datatype as auto number, so you may check for this. Or in other case you can take all the required fields inside the data view.