Hello native English speakers.

He advised the House to behave like the second Chamber of a modern state which they were supposed to be.(original)
Query1:
Is the original grammatically correct?
I understand the original as:
He advised the whole members of House to behave in the same way the whole members of the second Chamber of a modern state (behave), people supposed them to be member of the second Chamber of a modern state.
The exact query is :
Is my guess correct?
Who does the pronoun "they" refer to? (or who does the "them" (in my version) refer to?
Query 2.
I guess: they or them = the members of House’ s behaviour, so ,→ in the original,
which they were supposed to be = people supposed the behaviour of members of House to be the that(the behaviour) of members of the second Chamber of a modern state,
or rather. the behaviour of House should be that of the second Chamber of a modern state.
Is this guess of mine also correct?
Query 3.
If both of my guess above are incorrect, then, the correct meaning of the "they" depends on the context.
however , I insist my second guess is somewhat right?

Question

Hello native English speakers.

He advised the House to behave like the second Chamber of a modern state which they were supposed to be.(original)
Query1: 
Is the original grammatically correct?
 I understand the original as:
He advised the whole members of House to behave in the same way the whole members of the second Chamber of a modern state (behave),  people supposed them to be member of the second Chamber of a modern state.
The exact query is :
 Is my guess correct? 
Who does the pronoun "they" refer to? (or who does the "them" (in my version) refer to?
Query 2.
I guess:  they or them = the members  of House’ s behaviour, so ,→ in the original,
 which they were supposed to be = people supposed the behaviour of members of House to be the that(the behaviour) of members of the second Chamber of a modern state,
or rather. the behaviour of House should be that of the second Chamber of a modern state.
Is this guess of mine also correct?
Query 3.
If both of my guess above are incorrect, then, the correct meaning of the "they" depends on the context. 
however , I insist my second guess is somewhat right?

Answer

States do not have chambers.  Legislatures have chambers.  In the U.S., the two chambers (or "houses") of the legislature are the Senate and the House of Representatives.  The "second" chamber would refer to the lower one, the House of Representatives.  The sentence is certainly grammatical, but could be more clearly written:
"He advised the House to behave in a manner suitable for the second chamber of the legislature of a modern state."

"They" is an incorrect word choice.  The correct word is "it":
"He advised the House to behave as the chamber which IT was supposed to be."
The House is an institution, not a collection of people, though it does have members.

Answer

Your questions aren’t phrased in a clear way but you seem to have some correct ideas.

It’s correct. ‘The House’ = ‘the members of the House’ = ‘they’

The House is the second chamber of a modern state and this fact implies a certain standard of behavior for its members. Behave in a manner consistent with that standard.