He [topic-は] a-little sideways [to-に] squeezed [and-て] seat [object-を] opened gave.
横に詰めて 'scooting/squeezing to the side.' 席を空けてあげた 'opened up a seat for someone' — 空ける 'to vacate' + てあげる 'did it for someone (giving).' A small act of everyday kindness on a train or bench.