I can read/write/speak english. But I'm still waiting the first english spoker that pronounce correctly his own lenguage
Hehe...
"Man'-duh-bl" is how I would pronounce it. It is a derivation of the english word "mandible", or the lower jaw of an animal. It may have a different meaning, derivation, and pronunciation in Spanish, but I'm pretty confident in my usage of my native language.

Hehe, can't help it, foreign guy telling me I'm speaking my language improperly... There is proper english and colloquial english, or more appropriately, conversational and written english. In english for instance, contractions are commonly used in conversation, but are generally to be avoided in proper written form. The same phenomena occurs in many languages, probably spanish, too.
Some 3,000 miles separates our eastern and western coasts, and we have probably 275 million people. We include people from cultures all over the world, and we have several dialects. This is not an homogeneous country with respect to the cultures we include, so naturally you will see differences in speech.