Project DB, please help me

Hello!!
First I’m sorry for my english.
I try to create Db for good performace and light possible.
This Db is for the website for make stores online multi language for all world.
You can see the report DB:

http://www.computereconomy.com/report/tables/index.html

And image DB:

http://www.computereconomy.com/report/diagram2.png

I know pedding some tables, like: special, invoice etc
I have some questions…
Is better 1 DB or multi DB? For ex.: Db products, Db clients, Db service ect
If better multi DB, is better 1 server 1 DB, or 2 or more servers in mirror?
How is better make modular DB?

I’m sorry for too many question, but I’m Beginner.
Thank you every one!!!