Change code to work with 20x4 LCD instead of 16x2

[osval]

try to understand how you print 1 row. you need to recalculate a new "peak" and print it in 2 rows
this might not be correct but I believe could guide you.

@Electrofinn

 lcd.setCursor(x, 1); // draw first (top) row Left
    if (peaks[x] == 0) {
      lcd.print("_");  // less LCD artifacts than " "
    }
    else {

if(peaks[x] >8) {        // hier print on 2 rows.
peak_2 = peaks[x] - 8;
lcd.write(peaks[x],0); // print on 1st row
lcd.write(peak_2,1);  // print remainder on 2nd row
 }
else {
      lcd.write(peaks[x]);    // here you would print on rows 0 and 1 a value that depends on the peak 
    }
}