buckskin has you on the right track. You sound like the idle mixture is too rich, which is safer for the engine than too lean of course. When adjusting the the idle mixture, turn CW to lean and only turn 1/8 turn at a time and test. Naturally shut down the engine during the adjustment due to the large meat slicer in front (propeller). Develop good safety habits now and they will reward you (and your fingers) in the future. After a few adjustments, re-tune the hi-speed and verify all is still OK. High end should be approx 3 clicks richer than peak. Your instructors will get into this more with you as your training progresses.

Come back to here if you have more questions. there will always be someone willing to help on any subject.

Welcome to the insanity. Just go ahead and drop off your wallet at the LHS.