Marketing does not fix a business. It only amplifies a business. If you have something special, marketing will let more people know.
If there is a flaw in your business marketing will also amplify that. Marketing is not a silver bullet that will fix a business that has an inherent flaw.
What marketing will do: If you have a sound business and you can sell your product or service to someone in person. Marketing will help you find more of those people who might be interested in your product or service.
Make sure you have a good quality product / service at the right price and with great service. Then only expand on your marketing.