Cell phones can be used to take photos of fossils, but one has to understand the limitations of the equipment and how to compensate for those limitations. That’s why my original post emphasized learning basic photography skills. Cell phone cameras and lower-end digital cameras all have a delay from the time you press the shutter or touch the screen until the photo is actually taken. These cameras also have slow shutter speeds in general. Both of these limitations can give your photos motion blur. In order to get around this, you need to be steady and ideally brace the camera against something solid.
Other than a basic photography class back in the 1970’s, I learned most of what I know from reading. I would suggest getting a book on basic photography and reading small bits of it before you go to bed every night. You’ll start picking up things as you go and you can always ask questions.
My son has been taking some outstanding close-up photos of live insects recently. I accused him of using a DSLR. He used his cell phone. He has the advantage of having learned photography by using high-end equipment and that has allowed him to make good cell phone photos. He even has a National Geographic nature photographer interested in his work.