i can change camera speed?

If you mean the actual speed of which the freecamera moves, no. There may be a script but the better option is keyframing. If you don't know what it does, basically you press k when you want the camera to be at that position at that frame, and do it again in like 50 frames at a different position. It essentially makes it so you can have a free cam with the perfect speed and fluidity.
if you mean camera speed as in the time multiplier of a replay, the , and . Keys speed up or slow down the replay. If I have completely missed your point, then make a request in the "Suggest a script! 2.0" thread inthe Lua scripts section if the forum. Chances are some awesome guy named Psycore will have it for you within the day or will tell you why it's not possible and point you to some alternitaves. hope this helped :3