I'm not a native English speaker but I've recently moved to the US. I've been noticing that when people say "I'm going to" (or I'm gonna), a lot of people here always pronounce it like "I muh-nuh", so apparently this is a normal thing to say where I live, but I had never heard it before.
How common is it? Is that how you're actually supposed to pronounce it, and as a non-native speaker, do you think it's a good idea to learn to use it and talk that way, or I shouldn't imitate this at all?
Thank you in advance.