I feel for your frustration, excellent advice here though regarding the three main points ...who you are, where you are, and what your intentions are. also pre-fixing any initial RT with the word "Student"
I fly mainly in the US, and the majority of the controllers (especially in busy airspace) come at you with rapid fire RT !
It used to get me well flustered at times, so much so I have actually had some not so nice exchanges with one or two of the more abrupt controllers who show little tolerance when asked to "say again"....I once said to one pretty obnoxious guy that if he tried speaking English I might understand what he wanted me to do !..not to be recommended I got the number of the tower to call once I had landed..and got my head chewed off..
Now I've learned to slow them down a little by announcing - "low time pilot" followed by the usual RT. it seems to work.
Also works on the ground at the bigger more busy airports, If I'm flying to an airport where I know that ground will have me driving all over the field to get to the GA ramp, even if I've been there before, I usually announce "unfamiliar with field, request progressive taxi please" greatly reduces workload and lets you concentrate on watching for other traffic movements around the place.
On the whole controllers on whatever continent you happen to be flying are your friend and there to help.
Good luck, your radio work will soon click into place and you will wonder what all the fuss was about.
