This certain MySQL database organisation
You can approach this by creating the relevant foreign keys so you can use relations in your databases.
Here is a nice read about relational databases.
I strongly recommend it for you to read it, sou you can get the hang of the relational design idea.

Edit:
In your particular case i would to this:


Products (id, product_name, added_timestamp, seller_type, seller_id)
Individuals (id, name, last_name)
Companies (id, company_name, company_number, company_address)


where seller_type can be either 'i' as Individual or 'c' Company, and seller_id is the corresponding foreign id.