Questions to French People regarding a student project

[Sweric]

Hello Everyone!?

I'm new to this forum but I'm in need to reach people in France who is raised there and their view and experience on certain things.

First off, I'm currently working on my master thesis. I study digital marketing and im setting up an fictive "marketing campaign" for a company which offers payment of invoices and bills with credit cards. Some questions may be dumb, sorry in advance.

I have a few questions i would like to ask and see your view on some things.

1: What is your view and the general view on credit card usage? Is it a normal thing to use in France?

2: When is the most normal "payday" in France? I read somewhere that its up to the employer when to pay out salaries once a month but correct me if im wrong!

3: Are credit card usage different based on income? The higher the income the smaller use of credit cards?

4: Which card giver is the most popular one? Amex, Visa, Mastercard?

5: Would you like a service where you can pay bills and invoices with an credit card? (It works for companies as well)

6: Of course Paris has the most users of credit cards but is there any other town or area where there could be high usage of credit cards? Maybe along the French Riviera?

Thanks in advance for taking your time answering these questions! It helps a lot!