Volume not reducing

I have 3 tracks ready to mix and render I want to lower the overall volume before doing so but no matter how much I lower whilst it shows the reduction on the screen it plays back at the high volume

Weird… Did you try the Amplify effect with negative amplification (attenuation)? Try something drastic like -20dB on all of the tracks.

Mixing is done by summation so you’ll have to reduce all of the tracks to about 1/3rd (by about -10dB).

Or, you can export-as floating-point WAV (which virtually has no limits), then import the “loud” WAV and run the Amplify or Normalize effect to bring it down before exporting to your desired format.

…You shouldn’t keep the “loud” WAV because DACs are limited to 0dB and it can clip (distort) if you (or someone) plays it at “full digital volume”.