Here the word "heart" refers to the emotions. This means that God caused Titus to love them. AT: "who made Titus care for you as much as I do" (See: [[rc://en/ta/man/translate/figs-synecdoche]])
Paul is referring to his asking Titus to return to Corinth and complete the collection. AT: "For he not only agreed to our request that he help you with the collection" (See: [[rc://en/ta/man/translate/figs-explicit]])