Simple Database Design - Any Suggestions?

Question

I built a sample non real-life database for an automobile agency. The agency have some sellers, cars models, and buyers. I have to keep track of all of them.
These are the process i have taken while designing:
Normalization 1, 2 and 3NF and Relationship one to one and one to many...
Italic column is Primary Key...
The database not realistic, i did it for practicing purpose. Please look at the schema and tell me do you think its ok so far? or the design is wrong?
Here is my schema:
Seller table stores seller information:
*Seller Table {+SellerID+ (number), first name (text), last name (text), address (text), city (text), CountryID (foreign key), date hired (date)}*
Customer table stores customer information, customer can deal with one seller at a time while a seller can deal with more than one customer at a time:
*Customer Table {+CustomerID+ (number), first name (text), last name (text), address (text), city (text), CountryID (foreign key), SellerID (foreign key) }*
Car table stores information about cars available:
*Car Table {+CarID+ (number), manufacturer (text), model (text), car year (text) }*
Purchased car table hold information about customers who purchased a car and type car has been purchased as well as the date of purchase (date purchased relies on both field CarID and CustomerID:
*Purchased Car Table {+CarID+ (foreign key), +CustomerID+ (foreign key), date purchased (date)}*
OR
*Purchased Car Table {+PurchasedCarID+ (number), CarID (foreign key), CustomerID (foreign key), date purchased (date)}*
*Country Table {+CountryID+ (number), country name (text)}*
A customer and a seller can store several phone number:
*Phone Table {+PhoneID+ (number), CustomerID (foreign key), phone number (text)}*
If i want a seller to store more than one number, will i have to make a new table that stores sellers phone numbers? Or there is another better way to do it?
Note: i created country table and phone number table since they are considered multi-valued fields. To achieve 1NF, i must let every field in the table (e.g. Seller, and Customer) be atomic.

Answer 1

You need to study normalization and the concepts underlying 3rd, 4th, and Boyce-Codd normalization.
This forum is not an appropriate place to teach such a class.