It's the lowest string at 1st and 2nd fret where the buzzing noise always occurs

But after three days of playing, I started hearing some buzzing sound and the buzzing noise got even worse after a week

Then he took a couple measurements and said that the buzzing noise came from a couple frets that sat way higher than they needed to and the out of tune fretted chords were caused by the saddle that was off in its place by more than 1/8" of where it should have been positioned