"front row seat" can mean you are literally in the front row of something. But in this use it means that the person has been close to an experience or event. In this case they have been close to people who have been heartbroken and they have worked with these people. For "melting spot" I only know "melting pot" which means a place where people from all over the world come together. So New York is a melting pot because people from many different cultures and countries all live there. The last part, "as you'll soon discover, how much time is now up to you", means that when it comes to healing the person will realize that only you know how long it will take to heal. You are the person who determines how long it will take to heal, no one else. I hope that helps.

前排座位 最热的地方？melting是让人怜爱同情的意思 melting pot 是熔炉 melting spot不太确定… 因为你很快会发现，时间的多少取决于你。