I suppose u mean overflow tank is your main tank overflow compartment?
If that's the case yes.Will flow to the compartment level then down to sump.It's not rise up again la bro.It's back to main tank via return pump!
I suppose the end of sump u mean is the last compartment where your return pump is.
To solve that problem,add more water into sump.Higher the water level is at the last compartment,lesser the water fall sound will be.
Best if u can provide pics to show us. And we can give u a more appropriate answer.