Dungeon God Ragnarok

Jonathan North, an ordinary boy who falls for his fiancee was rejected instantly by her. He needs to defeat her if he wants to marry her. He battled her 13 times in 4 years and never won a single time. He was suggested to go adventure in the dungeon, however by going there e got betrayed and framed by his enemy. And was thrown under the deepest well of that dungeon which is known as the well of absolute death. Because nobody could crawl back from that hell. Then, how will our MC survive? Now, that's something interesting story to tell...