Hello Sofia,
This addon is meant to be used with a mouse. So if you use touchpad on your Mac, then it's not gonna be useful.
If you do have mouse, make sure to visit Options page where you can setup what mouse button is used for scrolling and where you can test the scrolling (in the right area).
If you have more questions, you can contact me directly on my support email.
Best regards,
Juraj Mäsiar

Hello,
I'm not sure I understand...
Could you write me email with more details?
Also, by default the addon emulates dragging scrollbar - so on long pages the speed will be faster. But it can be changed in the Options page.
And second question, was this working before? I released new version recently so maybe I've broke something...
Best regards,
Juraj Mäsiar

Hello,
The left button scrolling is very hard to do right. The web is full of badly optimized pages so be careful if something stops working (like editing cells in web Excel/spread-sheets).
The text selection cannot be improved, but you can change the way you select the text - if you use "double click + drag" then the text selection will select whole words, not just letters. And triple-click usually selects whole block.
Using these two techniques should help you with text selection.
But I'm planning to improve the left button scrolling to be more compatible on web.

Best regards,
Juraj Mäsiar