That was a very good first effort!
As you've asked, i've included some tips that may be of some benefit to you in the future.
little tips:
1. To add more periods to the "Loading" all you have to do is use a ; in between print commands to avoid having to redraw the whole thing.
2. Always use vsync 1 at the end of a loop if you are drawing stuff or checking button presses as in your case.
3. Only 1 Btrig() per loop is needed. Just assign it to a variable once per loop. Extra function calls will slow things down in more complex programs.
I've also condensed the separate 'beep' functions into a single function using some math trickery. That's not really necessary, just showing you a trick. Whenever you see repetition in a program, there's almost always a way to simplify it.
(on second thought I should have stored the button values into an array to avoid using pow() in the main loop, oh well
)
Here's the source if you want to see the changes I've made. Once again, that was a really good first effort, much better than mine.