Hi Candylover,
'African' is very broad and covers a range of diverse peoples and cultures. If your essays are so short then I suggest you concentrate on just one African culture such as Ancient Egypt. There is such a wealth of knowledge about the Egyptian civilisation, and it is all so readily available, that must be a good start. However, you can't detail the 3000-year history of Pharonic Egypt in just a few paragraphs or pages. You could just concentrate on a few highlights such as pyramid building, mummification and the 67-year rule of King Rameses II.
The medieval trading centre of Timbuktu is one African city worth considering as are the trading routes across the Sahara. The travel memoirs of the Moroccan traveller Ibn Battuta are fascinating and well worth reading from the Internet or your library. Ibn Battuta spent his life travelling 70,000 miles around Africa, Europe, Russia, India and China in the first half of the 14th century and his travelogues are full of humour and detail. Ibn Battuta crossed the Sahara with salt caravans and he visited many African cities. His observations, thoughts and experiences are a very good record of North Africa and it's peoples over 750 years ago.
If you are unsure how to approach your essays, or have difficulty finding a topic to study, then perhaps you should talk with your teacher. After all, they give you these essays to encourage you to do your own research. That's how you learn and gain an education.
Look up and read Ibn Battuta. Good luck.