Hello everyone

I am a green hand in the International trade .I am always do hard work ,I send more than 100 letters every day .But the effect is poor, fo r3 monthes there are little people answer the letter and almost nobody keep contact with me for business.
I really do not konw which part is worng?I am puzzled with this job.
Please help me and tell me what can I do to have successed in the job.

Many thanks !