Product Import & Export

Hello,

I am setting up a magento shop with magento verion 1.9.1.1. and I am facing some troubles regarding the import and export of products.

This is the theme that I am using: http://sebian.demo.arw.tf/fashion/?___store=fashion_es

To be specific: These are the troubles:

1. I have exported the product cataloge of the theme using system -> impoert/export -> data flow profiles -> profiles.
2. I have modified the exported .csv file, meaning I have added some own products to the .csv file but I didnt change the columns of the exported .csv file.
3. I have tried to import the file, but I get error messages saying, that the "sku" column ist no filled - but the "sku" column was not empty.

Right now, as a mangeto newbie, I am trying to understand how the whole thing regarding products, catalogues work and as mentioned before the import and export of products.

So, I have some questions:

a) Where do I get useful Information on the topic: Import and Export of products?

b) What is the general procedere for import and export regarding products and catalogues in magento?

c) How do I let the product images appear in the shop? Also in the above mentioned theme?

d) If I use a theme, do I have to take the given .csv file and update that file with my products or can I use a complete customized and individual .csv file with customized columns in the .csv sheet?

e) Can I use anothe .csv file than the file of the theme I have installed before?

f) Which other useful information do I need regarding this topic? Are there good and helpful sources? ( I have already googled but couldnt find something that would give help in my case.)

Could you help me out?

Let me know if you have more questions or need more infromation from my side.

Kind regards,
sjp