this sentence can have two meanings, depending on context and pauses and intonation stress

(Hotel yang baru) dibangun oleh kami The new hotel is built by us

AND

(Hotel) yang baru dibangun oleh kami the hotel is just finished built by us or the last hotel recently built by us

Is this ongoing, as in “the new building is being built by us”? Or, did this just happen, as in “the new building was built by us”?

What's the functionality of the word 'yang' in the sentence? Is it grammatically necessary?