Hi Kasper, for changing levels maybe you're after the Amplify effect, which can change the levels by a fixed amount, or the Envelope effect, which changes levels by a changing amount, or Normalize, which amplifies the whole file based on the original levels, or the Compressor, which changes levels based on the input levels, or the Equalizer, which changes levels based on input frequencies. For mixing, try Paste Mix, Mix with File, or check out MixPad.