You have to read some books on astrology.
Retrograde means backward moving.
Rahu and kethu move always backwards.
There is nothing extra ordinary.
Prosperity of rahu dasa will depend on how the
owner of house where Rahu is located.
Suppose Rahu is in Mesha,if Kuja is placed in
kendra from Lagna,Rahu dasa will be very good.
If Rahu is seen by a good planet,then Rahu dasa
will be good.
If you are suffering in Rahu dasa,you have to do penance
for one year to improve life. email@example.com
Rahu and Ketu are always retrograde. Retrograde planet is just a phenomenon where the planet is perceived to be moving backward. Many Astrologer debate on it as how to judge retrograde planets. But,As I follow, System Approach Astrology, where it is said that Retrograde planets shall also be considered in the same way as other planets, only transit effects could be prolonged to due to planet’s retrograde nature. Stronger the Rahu, better the Result. Ofcourse, sign placement and any other benefic aspect or negative affliction shall be considered.