VW Polo 2012 1.4 makes noise on gearbox but when clutch is pressed it gets silent. i have replaced clutch kit but noise still exist.

SOURCE: clutch noise and stiffness

it sounds like your clutch release bearing has or is colapsing.when you press the clutch the release bearing is under the most load hence the noise.gearbox out i,m afraid.Can you still get gears ok ?.Also the pedal box,s are prone to break on polo,s ,the symptom for that is like a squashy pedal and hard to get gears.if you can look up at the top of the clutch pedal where the cable mounts see if the bracket the cable fits in to is broken away at the top.

SOURCE: VW GOLF 1.4 1999 S. Gearbox makes whining sound at idle

No good news on this one I think
Your whining sound problem is the Layshaft bearings in the gearbox are badly worn. It also seems that the baulk rings are damaged on 5th gear.
John

SOURCE: how to change gearbox oil for vw polo 1998 mk3

There should be a 17mm allen plug at the bottom of the transmission. The filler plug is the same size allen plug on the end of the transmission, visible thru the driver side wheel well.

SOURCE: Hi, need diagram of 1997 VW Polo diesel gearbox

Hi Paul, Most of these gearboxes were almost identical for vw during the those years, some manuals are available free from this site
http://carservicemanuals.blogspot.com/search/label/Volkswagen
Hope it will help you out.
Dave

SOURCE: Where is the gearbox oil filler plug situated on a

i take it this is a uk spec car.(manual)..its on the side of the gearbox,a square topped plug it is also the oil level,when it stops flowing out its full.