senjahunter,
You have received good advice already from some of the most experienced bow hunters here on this forum. Typically, the majority of bow hunting is done from hides over water, mineral, or food sources. Your longest shot in these scenarios should be 30 yards or less. This is done deliberately to ensure that you have a very make-able, ethical shot opportunity that will result in a well-placed arrow and a quick recovery. You should be well-practiced and comfortable to 30 yards. You should also limit your shots distance to what you are confident with. From hides, shots of 20 yards and often much less are possible if you are patient.
As lpace stated, spot & stalking may require longer shots possibly 40 yards and beyond. We encourage our bow hunters to get out of the hides and stalk when the conditions dictate success. Taking an African animal via spot & stalk with a bow is the ultimate challenge and reward. With that, it is also important to realize that spot & stalking is going to be much more challenging than hunting game from the hides. Be prepared to get some acacia thorns in your hands and knees, and some dirt on your belly if you are going to attempt any stalking. Your shot opportunities will be much more limited stalking. However, there are certain species that are more stalk-able than others. Your outfitter/PH should be able to advise you of your best chances at certain species. Above all, get ready for a lot of fun! Africa is a bow hunter's paradise!