Learn French: Quant à mon frère, il a construit ce meuble lui-même. - As for my brother, he built this piece of furniture himself.

The word lui-même is an emphatic pronoun used to stress that he did the work personally, without help. He didn't build himself (which would require a reflexive pronoun), he built the furniture. To show this emphasis, you attach -même to the stressed pronoun lui.

Could we put lui-même right after the subject, like il lui-même a construit?

No. Unlike in English where you can say 'he himself built it,' French emphatic pronouns like lui-même almost always belong at the end of the clause or sentence. Putting it directly after the subject pronoun is grammatically incorrect in French.

Why is Quant à spelled with a 't' instead of a 'd'?

Quant à is a fixed prepositional phrase meaning 'as for' or 'regarding.' It is always spelled with a t, which distinguishes it from the question word quand (when), even though they are pronounced exactly the same way.

Why is ce meuble translated as 'this piece of furniture' instead of just 'this furniture'?

In English, 'furniture' is an uncountable noun, so we have to say 'a piece of' for a single item. In French, un meuble is a standard countable noun referring to one specific item (like a bookcase or a desk). To say 'this furniture' collectively, you would use the plural ces meubles.