Adomako,
Marketing revenue is not a service, per se. To be considered as a freelance worker, it is generally assumed that you have a service to offer and that you are a legitimate expert at that particular skill.
If you are a marketing expert, that's one way you could define your working niche. But "marketing revenue," is not a service. It's just two somewhat related terms ... revenue being the money you take in when you own a business.
That said, you need to say a lot more about your skills, your education and your work background to convince a client to hire you.
You should probably research markeing work and see where you fit in. Once you choose a starting place, study that skill set for as long as it takes to understand the skill and the marketplace. One thing that helps is to review Upwork profiles -- in your case, Upwork profiles done by marketing experts. See what they have to say about their skills, their jobs, and how their skills will help their clients.
Good luck. I do know what poverty looks like. I wish you a speedy change in your circumstances, but I warn you that marketing is not something that you can learn overnight. What you can do, however, is learn quite a lot by researching on the Internet. If you have a computer or a library that allows you to use their computer, you can teach yourself a lot fairly quickly.
Good luck.
