Complex sentence: Trump's first big deal in Manhattan was the remodeling of the Grand Hyatt Hotel in 1978 next to Grand Central Terminal from an older Commodore Hotel, which was largely funded by a $70 million construction loan jointly guaranteed by Fred Trump and the Hyatt hotel chain.
Split into simpler sentences: Trump's first major real estate deal in Manhattan was the remodeling of the Grand Hyatt Hotel in 1978, located next to Grand Central Terminal. The building was remodeled from an older Commodore Hotel, and was largely funded by a $70 million construction loan jointly guaranteed by Fred Trump and the Hyatt hotel chain.