Hi Seenu,
If you want to check the logged in username, you can put an external breakpoint in the create_entity method and check the sy-uname in the debugger. Advance with one step forward and when you are inside the FM of backend, you can check the sy-uname in backend system. If SSO is correctly established between gateway and backend system and there is no user hard coded in the RFC destination, both sy-uname should be same.
Please check this link Trusted RFC creation between Gateway (Front End) and ECC (Back end) servers
Regards,
Ekansh