Why do people pronounce "f***ing" like "f***en"? [duplicate]

I'm not a native English speaker so I might not be exactly accurate with this, but whenever people (e.g. in films) say fucking, it sounds something like fucken.

There's no "g" at the end and instead of "i", I hear "e" (like in the word men).

Why is that? Am I that deaf or is the pronunciation really different from what the spelling would suggest?

If it is, why do people pronounce it this way? Why is it different than any other word ending with -ing (e.g.looking)?

"Fucking" would have less impact if pronounced correctly in so called "Queen's English", which is associated with formal speech. Where it is not usually part of a person's pronunciation, and speaker will sometimes consciously change "ing" to "en" or "un" to affect an accent more strongly associated with profane language.

Popular media / actors know this, so they also pronounce it in that way - and this is what you are hearing in films and T.V. shows. Arguably, this exposes native speakers to the pronunciation and teaches them to pronounce it that way in a feedback loop.

That is not to say people do not pronounce "Fucking" with an "ing" ending. Many people do.