About "Z" Visa

I am studying in China and I'm from Bangladesh. I am doing internship in a company. My company is interested in joining me as a full-time employee. Now I am on a student visa. I will graduate in July. My student visa will expire on August 1. I can't stay in China after August 1. So I need an employee visa. How can I easily get a "Z" visa? What papers should I submit to the embassy? If I go back to Bangladesh and try to get a “Z” visa from the Chinese Embassy in Bangladesh, would it be easier? What kind of difficulties might be? please help me