Complex sentence: Barry is also in a better place with his mom's death as he finally understood what the prayer she use to say meant and is reunited with Iris and gives Batman (Bruce Wayne) a letter that Thomas asked him to deliver to his son.
Split into simpler sentences: Barry is also in a better place with his mom's death, and is reunited with Iris. He also gives Batman (Bruce Wayne) a letter that Thomas asked him to deliver to his son.