You may be dumb in one field but you can be great in another. A fish always feels dumber watching a monkey climb a tree so easily and knowing that it could not climb. Find a field where you can be good. Everybody is good at something. Bad grades do not necessarily mean that you cannot get rich. Getting rich requires financial and economic knowledge, it doesn't necessarily matter how or what you have studied.
Last but not least, you can also earn money online by building an online community, although the monetization strategies you can pursue will vary a lot depending on your goals. You can build a community with a blog, for example. You can also build an online forum and charge people for membership. You could even build up a Facebook group and use your influence there to sell and promote products.
If you're running on fumes, financially speaking, but you have some money coming your way soon, consider pawning something of value to borrow fast cash. Of course, to get those items back you'll need to pay back the loan with interest. If you don't pay it back in time, that you'll lose the item. If it's really something that has a lot of intrinsic value to you, don't do it. But if it's something that doesn't, you can certainly consider it depending on your situation.
Market your course: The beauty of using a course to make money online is that you can continue to sell it for as long as you’d like. Look for niche communities on Facebook, LinkedIn, or Reddit that might benefit from your content. Guest post on relevant blogs and sites. Look for anywhere you might be able to get in front of the right people. With just a few hours a month you can continue to generate sales.