Put the verbs in the wright form:
Here I am ( to reply) to your letter which ( to arrive ) two days ago,
before ( to leave ) for Rome. I ( to tell) yesterday that the company ( to send) me there next week for a business conference. If I ( to know) about it earlier I ( to inform ) . Anyway I ( to ring) you up as soon as I ( to can). By the way, I met John Marshall who ( to work ) for the previous two months on some interesting plans.