If my signal that was started just few days back shows an average slippage of 6 and 9, which I guess is not that good...
Does that mean my broker is not a good one and I must change to another broker to get a better slippage?
These are quite large values, yes.
I am happy with my broker, but need a better slippage rate...
What causes the slippage to e too high?
Will it get improved upon subscription?
Can I change the broker I currently use for my signal, and keep the current details of the signal unchanged?
You cannot change the broker you use for a MQL5 signal I am afraid.
If you change to another broker you will have to publish a new signal.
Slippage is the difference in price between brokers, due to different sources of liquidity pools used.