It's good to see two ffishers helping each other out!
First, Rudolfbeer, why don't you visit
http://www.sexyloops.com for advice on your casting. They have everything on that site, including some really esoteric stuff you will not understand at first. The rod you have is a fine casting tool and there is no reason why you should not get distances of 20m and more with little effort. 20m is most certainly in reach without double hauling.
Although you don't really say much about how you fish, bear in mind that if you can see the fish, they can also see you. Try a bit of stealth and watch your shadow. Try to avoid showing your profile against the sky line. You will also have more success early and late in the day.
Try to stick with the floating line at first. It will most certainly make casting easier and don't be afraid of long leaders. In a dam the shortest leader that I will use would be about 10 feet, consisting of 8ft of leader (usually 3X tapered) and about 2ft of 3 to 4x tippet. I will go as long as 20ft if the water is clear and deep and the day bright. I never use a strike indicator. Watch the end of your line.
Although a black wooly bugger or policeman is a reliable fly, remember that there are many ways to skin a cat. Why not try a team of flies by simply attaching a small (#12 to 16) buzzer pattern to the hook of the wooly bugger with about 30cm of tippet. Believe me, you chances are much improved. Or try a blood worm imitation (San Jaun worm) or flies like the Gold Ribbed Hare's Ear (the most popular nymph pattern on earth), the Connemara Black, one of the darker spider patterns or a Pheasant Tail nymph? Or try a dry fly (DDD), an emerger pattern (Klinkhamer) or a snail pattern fished just under the surface. The possibilities are endless and learning what works under what circumstances (weather, temperature, wind, time of day) is what make flyfishing such a wonderful persuit.
And last of all, remember that there are many species of fish that will take a fly. Not far from Pretoria is the Vaal River, full of yellowfish that are willing fly takers. But that is another most fascinating subject.
