I hear water flowing from the "pump" outside the furnace, that has a tubing connected to a train tube by the sink nearby.
I looked inside the bos ("pump"), there is some solution (like antifreezer) inside, but vary shallow. What should I do to silent this pump, or to fix this problem?

The term "condensing" furnace gives you a clue. Your furnace is 90%+ effective and extracting all the heat causes the remaining water vapor to condense into a drain line and is pumped out, usually through the same pump used for the AC. This is a normal circumstance and most likely not a problem. If the water overflows from the pump, you have a stuck float or a bad pump motor.

http://www.gogeisel.com/geiselonline/support/Bryant/340MAV_350MAV_355MAV_OM.pdf

Propylene gylcole is added to prevene winter freeze up if the furnace is to be left unattended in freezing temperature. Read all the above document and you'll see the instructions.