Set the correct input device, see A 'select input device' (if your using JACK switch it ALSA to select device, then back to JACK)

Turn the capture level up, see D 'capture level up'. Don't confuse Capture with Mic. Mic sets the volume of Mic 'thru' but not the record level.

If frugally installed set temporary directory outside of SaveFile . Go to edit > preferences > directories set to something like /mnt/home/audacity-temp

Select view > 'show clipping' highlight any part of the recording that has distorted due to input being too high.

If recording multiple tracks you may need to lower latency - otherwise new track may come in too soon.

Use Jack to monitor if your system is recording continuously without gaps (due to not enough processor time allocated, or not fast enough processor).