Hello, EnriqueM30. I can give you some tips about how to win Mr. Trumpson's battle. Check them out:
Mr. Trumpson's battle will end when his HP goes less than 50%. Probably Lovesdick will die because of Mr. Trumpson's skills. You need to focus on keeping Scarlet alive because he has the most powerful area skills (try to alternate between Tower of Babel and Meditation Lvl 2 to avoid running out of mana. Also, always have more than 250 MP because opponents have mana drain) and use Lynx to support the team by using his Ultimate Healing skill. If the fight goes bad, use the Miracle Potion obtained on Gleen's Side Quest. After this battle, some cut scenes will come up before the game ends. Watch all of them because you'll get a surprise that I'm preparing!
I hope they help you. If you need extra help, you can join Discord so that I can help you based on your level and skills.