This is how I would write it. Last week, we replaced the old?? lampshade of the wall lamp in the living hall at main building with a new one .
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Mr. Tomliving hallYou could write living room or, just hall. Choose one of the underlined parts.
AnonymousLast week, we have replacedOof! Here's a mistake already. In English we don't combine a mention of the time (last week) with the present perfect tense (have replaced). You need to remove "have". Last week we replaced... Note also that you don't need the comma.
Anonymousthe existing lampshade of