Actually "good night" means "iyi geceler"
good= iyi, night =gece [we use it as plural, night(s)=gece(ler) ]
Allah rahatlık versin= Allah(God) give you peace [ But usually it is said to someone who goes to bed ]
sweet dreams =tatlı rüyalar
sweet=tatlı, dream(s) = rüya(lar)