AADSTS9002313: Invalid request when trying to get auth tokens via Postman

Question

Dear Madam/Sir,

I'm currently trying to to use Microsoft Graph to read and write Emails on behalf of a user by following this documentation:

https://learn.microsoft.com/en-us/graph/auth-v2-user#3-get-a-token

But I couldn't continue as I retrieve constantly this error while getting a token

{"error":"invalid_grant","error_description":"AADSTS9002313: Invalid request. Request is malformed or invalid.\r\nTrace ID: 3765634b-7e56-4e17-b8ba-2fa8b7057c01\r\nCorrelation ID: 6f72db61-e14a-486f-b972-8a0c4600dbd2\r\nTimestamp: 2021-05-05 07:01:02Z","error_codes":[9002313],"timestamp":"2021-05-05 07:01:02Z","trace_id":"3765634b-7e56-4e17-b8ba-2fa8b7057c01","correlation_id":"6f72db61-e14a-486f-b972-8a0c4600dbd2","error_uri":"https://login.microsoftonline.com/error?code=9002313"}  

Here is a screeshot of my Postman entries:
Body

Header

Thanks for the help in advance.