How quickly can a hot air balloon climb?
It very much depends on the balloon, but 2 metres/second in actual flight is pretty typical, while most are capable of something like 3-5 m/s ascent/descent if required. Ascent and descent speeds are normally about the same for a particular balloon, but this isn't a hard and fast rule

"sport" balloons being are capable of moderately less comfortable ascent/descent speeds in the range of 5 to 10 m/s