When removing noise using Adaptive Noise Reduction, it leaves some noise at the beginning

Also, when increasing the volume of short bursts of sound, it no longer sounds like the original, which is very poor.

Further to what Mike said, you have to realise that in ANR's name, the 'Adaptive' part is significant. It has to read a part of a file before it can react to what it analyses as noise, and this takes a finite amount of time. Also, this applies to changes of noise within the file, so if the nature of the noise changes abruptly at any point, the same thing is likely to happen - it won't catch the start of it.

Adaptive Noise Reduction works best on sources where there are gradual changes of noise; in principle it can handle this better than the 'normal' NR, but it's not as good for constant sources. And all NR is at best, a compromise - if you have a very poor signal to start with, then any NR you do to it is going to make that more obvious, I'm afraid.

Adaptive Noise Reduction takes a second or so to kick in. You can't change this so better to use DeNoise or Noise Reduction if you want something that works immediately from the start of your audio.