Thank you for the advice! I will try the tuning recommendations you have and check the thumb string tuning peg.
In regards to action – I meant that the action (I believe) is too high. When I play there seems to be a lingering buzzing sound that muddles the melody notes. However, I’m not sure exactly how to diagnose if it is high at the nut or the bridge. I suspected the nut but while inspecting it, it looks like it might be higher towards the bridge (at the 10th/12th fret area).