Who is that fat man? Who is that fat man?

This is a correct sentence but "fat" can usually come off really rude. There's really no way in English to describe someone's weight without coming off rude. It's okay, though! I just wanted to let you know.

Who is that fat man? Who is that fat man?

This is not incorrect but it is considered impolite to say someone is "fat." Unfortunately we don't really have a way to describe a person's weight that is considered polite, although we might say that somebody is "overweight."

Who is that fatlarge man? Who is that large man?

We don't really use "fat" to describe people any more in the US.

He is My'smy employee. He is my employee.

He is My'smy employee. He is my employee.

Unless there is a person named "My" who you are referring to.

He is My's employee. He is My's employee.

Unless "My" is a name, you would get rid of the "'s" and the capital letter because "'s" is usually used when you're using a name. You're right that it suggests that something is yours, but the "'s" is used when talking about someone else.

He is My'smy employee. He is my employee.

Since "my" already expresses possession there is no need to have an apostrophe here.

He is My's employee. He is My's employee.

Is My the name of a person? If so, then this sentence is correct. If not, the correction would be this: "He is my employee."

They are air hostesseflight attendants. They are flight attendants.

They are air hostesseflight attendants. They are flight attendants.

We don't call them "air hostesses" but instead "flight attendants."

They are air hostesseflight attendants. They are flight attendants.

This is what we call them in the US.

They are postmenal carriers. They are postal carriers.

They are policemen officers. They are police officers.

They are policewomen. They are policewomen.

We don't really use "policewomen" but refer to women in the police as "police officers."

They are policewomen officers. They are police officers.