Hey Faaysal, try to reboot your phone first. If still a no go, better to check if landscape is part of the MIUI BETA changes. If not, please wait for the stable version as it might be part of the bugs. Please submit a feedback for the Mi development team to work on and add it in their stable version improvement.
If I'm wrong, lets wait for the other beta users to comment. :)
I already tried to reboot my phone a couple times but it didn't work, I also have sent a feedback. but after I read your comment I tried to reboot one more time and I don't know how, it's working.. this is soo embracing. thanks very much by the way*