The best way to understand cells better is to look at some through a microscope. If you don’t have a microscope yourself, try going to a science museum or try to raise money to get one for your school. You can also get microscope lenses that attach to a smartphone.
Once you have a microscope, put a plant cell under it (like from an onion skin) and try to find the nucleus and the outside membrane and the vacuoles. Put an animal cell under it (like from your own cheek) and try to find the nucleus and the outside membrane.
Bibliography and further reading about eukaryotes: