Complex sentence: To prepare for the role, he worked with a dialect coach and watched Obama's speeches to master his accent and manner of speaking, as well as learning how to write and play basketball with his left hand.
Split into simpler sentences: To prepare for the role, he worked with a dialect coach and watched Obama's speeches to master his accent and manner of speaking. He also trained himself to be portray the left-handed Obama, including learning how to write and play basketball with his left hand.