(1)  Be supposed to: it is believed/ said.

• It’s supposed to be the best restaurant available in the town.
• He is supposed to be a modern writer.
• He is supposed to be the richest person in the locality.

(2)  Something is supposed to happen = It is planned, arranged or expected.

• I am supposed to meet him at 10.00 am at the Hotel Casino.
• The attendant was supposed to keep the Board Room clean and tidy before the meeting.
• The train is supposed to arrive within 10 minutes.
• Monsoon is supposed to reach within a couple of days.
• You were supposed to come before 10 o’ clock .  Why did you fail to come?

(3) You ‘re not supposed  to do something = It’s not allowed or advisable for you to do it.

• You are not supposed to smoke here.  This is a smoke-free area.
• You are not supposed to park your car here.  This area is meant for doctors.
• You are too weak to do any heavy work.  You’re not supposed to do any heavy work.(i.e doctors have advised him against doing any heavy work)
• We were supposed to speak in English only within the campus of Federal College.