Who cares about competition? There's no need to worry about competition unless you need to be #1 in the industry. Otherwise being number 74 still has income and more than enough to live off of :)
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The site or the database? The database is actually quite easy:

ReviewInfo
- ReviewID
- TypeID
- Category
- DateCreated
- SubmitterID

Reviews

I can help you a ton, as I know database design very well. However, I need information about what is going to go in each table. Please include everything, payroll and the rest. I can design you it...

Okay, then this is what I would recommend, and yes it is more complicated than it has to be, since you're the owner.

Stores
- StoreID (P)(AI)

Products
- ProductID (ID to relate to other...

I would recommend combining a lot of those tables together, but it depends on how far you are going within those tables (how many columns).

You can link complaints to writeups into one table, as...

Transactions and Shipping is based off of that you are selling the products to the owner, who in return sells the products somewhere else. If you are the owner and just run the carts, then you don't...

I got you the first time, here I'll let you know what I meant and with the edits that you gave me (like no store owner, etc.)

Stores
- StoreID (P)(AI)

Products
- ProductID (ID to relate to...

Products is their current inventory and that is kept store to store, so storeID separates each row accordingly.

Shipment was for you, cause you ship them the goods, don't you?

According to your thumbnail, this is how I would make the databases:

Stores
- StoreID (P)(AI)
- StoreOwner
- StorePhone

Products
- ProductID
- ProductQty