Building built on Land gifted by father

My father gifted a land to myself and my brother in 2019. He himself bought the land in 2003. Myself and my brother obtained a permission to build a building on this land in 2021 and constructed a house and finished it in 2023. We sold parts of the building in 2023 ( 60%) to different buyer after completion of building construction. Upon consulting with a CA, they mentioned the underlying land is a capital asset ( long term) but the building sale cannot be considered to be a longterm capital asset. They have instructed that the capital gains from sale of the asset is short term in nature. I am of the belief that constructing a house or multiple houses on a land, should be considered enhancement/addition to the underlying capital asset, the land. So, the sales proceeds and any profits from the same should be in total considered longterm capital gain. Please advice if there is any legal precedence in this regard. Also I need advise on what all documentation is needed for tax filing