Where in the Berg will you be staying (bearing in mind that the high berg range is about 300km long)?
No1 should be the Ampitheatre (Royal Natal National Park/Witsieshoek) by the Chain Ladders or Beacon Butress Gully (there is a full write up on both on this forum, you can start at the Sentinal car park which makes it a fairly short hike, this will allow you to spend some time on the top, maybe hike right across the top and back again)
2nd I would say is Cathedral Peak (Didima nature reserve) via the standard route (this is a tough 20km hike, it has (b-grade I think) rock scrambling, it is advisable to get a guide from the Cathedral Peak hotel)
3rd I would say Rhino Peak (Garden Castle Nature Reserve, my personal favourite reserve) via Mashai Pass (this is another 20km day hike, its pretty tough as a day hike, but it is an amazing area, there is a pass description on this forum for this one, the KZN Wildlife website has a fair description of it as well). It may be worth trying to arange for a KZN wildlife guide here as there are usually some Basothos waiting at the top to try to get food and cigarettes from hikers (I chose the day that KZN Wildlife remeasured the path to do this hike (not deliberately), so I reached the escarpment at the same time as 3 KZN wildlife guys with big guns reached the top, so the Basothos left us alone, but they have been known to be quiet pushy with other hikers in this area. Don't let this put you off, if you take a packet of sweets for them, they will probably leave you alone, its also winter so they are less likely to be at the top of the pass at this time of the year).
4th would be a really tough day hike (26km up a difficult pass, but from the top you should be able to clearly see half of the southern berg and the entire central berg) is Giant's Castle (at Giant's Castle Nature Reserve).
There is a book (I doubt you could get it in Poland, but when you get to SA you should be able to get it, otherwise Amazon.com might sell it), Best Walks of the Drakensberg by David Bristow, it has detailed descriptions of all of these hikes (and many more) as well as maps and some details of the history of the area, I personally have found it to be very useful in planning hikes.
It is true that it should be well below 0 in August (bearing in mind that it is winter here at that time), it would probably reach about -8 at night at the top.
Btw you can download the maps (and photos of the areas) from
www.berg.co.za