Project 5 in the training

i cant understand the topic Advanced Graphs and Changing the sound of Buzzer

its quite simple.
in advanced graphs we are just using other graph options then line graph like scatter graph,stepped graph etc. and we can also create two different graph visualization in the same project.
in the changing the sound of the buzzer we are varying the frequencies of the buzzer so that the sound of the buzzer either increases when the frequency is high or decreases when the frequency is low.

Try referring to the documentations on graphs in this link:
You’ll find on the left side, links to different graphs.

For changing sound of buzzer, here the process is very similar to what was done for controlling the LED. Except for, we don’t need to connect a resistor to the buzzer like we did in the LED. It can be connected directly to the BOLT module.

for changing the sound of buzzer what code we have to write

Use analog Write function in your code in place of digital write
analog write function has following parameters
VALUE: The value ranges from 0 to 255.
PIN: Ranges from 0 to 4. You must choose the PIN depending on which pin your LED is connected to.
for more information check the documentation