Your english is fine, so no apology needed! Using an AI is going to be very individual. Everyone responds differently to the aromatase enzyme. Some may only need .5mg 2x a wk to stay dry on high doses of test, while others need to use it almost every day to get a dry effect. I think you have the right idea by starting low. See how you respond and slowly move the dose up if you are seeing too much fluid retention. Just keep in mind that wiping out too much estrogen will effect your gains. .5mg EOD should be the most you need if you are using about 500mg EW of test. Even that dose may slightly effect your ability to gain quite as much as you may have been able to gain with a lower dose of AI. Thats going to be for you to weigh out. Whats more important? gaining muscle or staying dry and hard? Remember that there are other ways to control fluid. Steroids make you more sensitive to sodium. Its ok to eat sodium on gear. You just dont want to have huge spikes of sodium through the week. Keep it consistent. And if you drink plenty of water, which you should always be doing, you will constantly flush your system, keeping you from holding too much fluid. 

As for needles, most people use a 23g 1.5 in pin for glutes and a 23g 1 in pin for quads. If you are very lean, you may be able to get away with using a 1 in pin for glutes, but you are better off sticking with something longer. You want to make sure that the depot is injected deep into the muscle. If it is too shallow, you can run into issues, like more pain and swelling. The irratation of a bad shot can last for a wk.