Not sure what you mean: it looks like it is working just fine. The Terminal in the bottom of your UI has output showing the app.py file has been run and is outputting the following:
HelloWorld
**********
That is the expected output for your program.
Is there something going wrong with what you were expecting?
the second line is not printing and how to get rid of the extra lines before HelloWorld
What do you mean by “the second line” it is printing 10 of the star (*) characters like you asked. Did you expect it to print something like this?
"*" * 10
That second line prints this:
**********
And the new line before the “HelloWorld” is printed by the terminal when you execute the command.
where it says /usr/local/bin/python3 /Users/mohamedgedow/Helloworld/Helloworld/app.py
on Mosh’s video he didn’t have anything similar
Yes he does, he types: python3 app.py
You are probably using the button which uses full paths, but Mosh manually typed that out (see screenshot):
Yes, what you have is completely fine and working as expected.
ok thanks very much 
If you want to remove the path from your terminal output, then use a coderunner extension in vscode, here is the setup