Show Data in Gridview based on selected Value in DDL ( API )

I need to add or fix the following point in the project:
1. In Issue Voucher page ( Add & Edit ):
• There are two drop down list related to this option (BENEFOCIARY NAME & BENEFOCIARY CATEGORY ) which are related to API from another system.
• If the user select a category from BENEFOCIARY CATEGORY drop down list, then it should show a grid view with following columns ( only Beneficiaries that are related to the selected category ):
o BENEFOCIARY Name
o BENEFOCIARY ID
o Check box ( selected by default )
• Show option to select all check boxes in the grid view or unselect.
• If the user select blank BENEFOCIARY CATEGORY, then clear the new gridview and hide it.
• The category ID is already exist in BENEFOCIARY Name API and you can get the BENEFOCIARY Name by sending the parameter category=( selected BENEFOCIARY CATEGORY )
• When click save should create for loop to select the checked BENEFOCIARY ID in the gridview .

2. Need to fix the scroll in the main menu ( check the attached picture).
3. Need to make the giedview in Journal Vouchers page, word wrap in the column General Description ( check the attached picture).
- All above pages are already exist in the project.
- Programming should be in ASP.NET and VB.NET
- Modification should be in the current VS 2017 project file.
- Project file and database is available upon request.