How to add and use multiple countries?

Hi!

Have been searching for the topic but didnt find an proper answer so far.

I am using the new business directory theme and need to use COUNTRIES as one listing (service) can operate in multiple countries. Therefore:

1.)
A service (listing) can be in multiple categories
A service (listing) can be available in multiple countries

2.)
When creating a listing, the new member should choose the right COUNTRIES of the WORLD he is offering the service in; next to his official company address. The input fields should are CHECKBOXES. Very important is that there it could be more than one country. So taking the “country” from the company’s address doesnt make sense as there is only one address/ one country.

3.)
Visitor should be able to filter the the listings by country via a DROP DOWN MENU. The country should be the available service in a specific of the company not the company address.

I guess everything should be possible in:
– General Setup/Registration ? and/or
– Listing Setup/Custom fields? and/or
– General Setup/Advanced Search

What are the right steps to get this work without having CONFLICTS with the “country” database key? Shall I create a new database key or can I use one existing? The videos under Listing Setup/Custom and General Setup/Advanced Search are not clear if there will be conflicts with “country” database key.

Thanks for feedback.
Best, Rob