When it comes to VDSL speeds, a large portion of this will be determined by the strength of the electrical signal on your the copper line (this is commonly known as "Line sync rate").
Chorus has a handy public tool to get an idea of the likely sync rate to your property. While this won't tell you an exact expected download rate, it does normally give you a fair idea what to expect. You can find this tool on their website:
For example, in the above screenshot, Chorus believe the VDSL sync rate will be approximately 18Mb/s download. Most MyRepublic VDSL connections will match this rate quite closely, especially via wired connections.
If you feel your connection isn't meeting this above expected rate, we can offer some further troubleshooting to try. Make sure you take note of your expected rate before we continue troubleshooting.
Next - How are you testing your speeds?