noise remove under Audacity v2.0

I set up noise removal as following after “get noise profile”:

noise Reduction (db): move the bar to right most point (maximum)
sencitivity (db): 0.50 move the bar to about the middle point
frequency: 0 move the bar to left most point (minimum)
attack/decay time 9secs): 0.00 move the bare to right most point (minimum)

this will remove most noise. Then I perform the same task mentioned above again for another couple times to remove minor noise.

If I move the bar closing to maximum under "sencitivity (db): " to remove noises, the mp3 file converted hear like a machine generated voice, not like a human being voice.

Are these are correct ways to remove noise? I have difficulty to set up these scales.

You are using very extreme settings.
Noise removal is always a balance between the amount of noise removed and damage to the audio that you want to keep.
The effect can work very well on constant low level noise. It does not work well on noises that change or high level noise.

Could you post a couple of short samples in WAV or FLAC format (about 5 seconds each) of (a) the noise that you want to remove, (b) the audio that you want to remove it from.