welcome to M9 friend... don't worry about your english... most of us here aren't that fluent either... but images go beyond words... it is what unifies the M9 theming community
about your mask problems:
icon masks --> when using the theme studio, go to icnos, click on the image you want to use as an icon on your browser window on the far right, then click on the mask option on the near right, click on the arrow that points downward and it will give you 2 tools to choose from, the wand selects all the same colors that are continuous with each other, while the pen selects 1 pixel at a time... you'll know that you've selected a part of the image when that part turns into a more purple/violet color... these purplish/violet areas are the parts of the image that will become transparent when you install the file in your phone
clock masks --> use the appropriately aligned part of the general background image as the background image of your clock... that way, you don't have to mask it at all
numbers mask --> sorry, i haven't done any... but i can send you some images already with masks as contributed by people who request themes from me... all you have to do then is to click on the appropriate image
post something if you're still confused... but i suggest you play around with your theme studio to see how things work for yourself... and always test your themes on your own phone... theme studio does not always give an honest preview... meaning what you see on the theme studio preview option is not always what you'll see on your phone
happy theming!