Hi Zijie,
I am sorry it's taken so long for you to get an answer.
YOUR FIRST QUESTION
"If I hire a market expert to help me do ground marketing in Spain, which means find Spanish Company, organizations, and Travel agencies, what type of contact should I prepare for him?"
YOUR SECOND QUESTION
"My company current located in China, and what language of this Contact should be?"
MY ANSWER TO YOUR FIRST QUESTION
Contact the following organizations (in both countries) to ask them that question to get a full view of what you need to do:
a) Spain Chamber of Commerce in China (or official representatives in China (consulate or embassy, specifically their trade department);
b) China Chamber of Commerce or official representatives in Spain (consulate or embassy, specifically their trade department);
c) Business lawyers here and there who are well-versed in international laws;
d) Tourism and/or Import-Export professionals in both countries.
MY ANSWER TO YOUR SECOND QUESTION
In both languages.
Not just translated, but really meaning exactly the same thing so that the person in Spain may understand exactly the same thing as if that person was hearing/reading what's in the contract in the original language, Chinese. Yes, write the original contract in Chinese, in your own language, first.
Hope this helps.
Cordially,
Marie