how to copy signals with desirable volume ?

Please explain yourself in more detail if you want a serious answer.

1. Down by reducing the deposit load below 95% (max)
2. Up by increasing your account balance vs. what the signal provider has. Signal lot size is adjusted from signal balance and leverage to yours.
3. If you had used this you would have found among many:
             Icrease lot size - General - MQL5 programming forum #2 (2018)
             signal provider has minimal volume 0.01, subscriber has 0.10 - how to change minimal volume ???? - MQL5 programming forum (2013)

How to copy

Make sure you've done everything as described here: 

How to Subscribe to MT4/MT5 Signal

https://www.mql5.com/en/forum/189731  (MT4)

https://www.mql5.com/en/forum/336422  (MT5)