"I prayed to Yahweh about my great trouble." Even though Jonah was praying to Yahweh, he used Yahweh's name here. This could also be translated with the pronoun "you" as in "Yahweh, I called out to you about my distress."
## he answered me ##
"Yahweh responded to me" or "he helped me"
## from the belly of Sheol ##
"from the center of Sheol" or "from the deep part of Sheol." Jonah believed that he was about to die and go to Sheol. He spoke as if he already had died and gone there.