Hi Vignesh,
Few resource that can help you .
https://medium.com/mendix/publishing-rest-apis-in-mendix-8a1feea99a71
https://academy.mendix.com/link/paths/33/Create-a-REST-API-(Micro-Learning)-
Also share screen shorts of error for us to help you properly.
Thx
Suggestion. Use Postman to get the REST working. To me the interface is intuitive and flexible and the errors are easy to spot. Once that is working then go into Mendix and make sure it is doing the same things (congirured the same).