have

How is "have" (or "has") commonly pronounced in FAST speech, in American English? Here are some pronunciations I am pretty sure about:
I have a girlfriend - /aɪ ɛv/, /aɪ hɛv/
I have seen it - /aɪ əv/, /aɪ hɛv/

Here are the pronunciations I am not sure about (I am considering the cases where the main stress is not on "have")
I haven't seen it for a while - /aɪ ɛvnt/, /aɪ hɛvnt/
I don't have a car - /ɛv/, /hɛv/
She hasn't seen it - /ɛznt/, /hɛznt/
I have to check it - /aɪ ɛftə/, /aɪ hɛftə/
He has to do it - /hi ɛstə/, /hi hɛstə/

All these when the main stress is not on "have", otherwise it'd be /hæv, hæz, etc/.

Can someone comment on this? Thanks.

improe my english

It's tough to judge one's own fast speech, but I think the most common fast speech pronunciation in the US would be /Ev/ or /hEv/.

Yes, I suspected so. But does such reduction (or "weak form") also apply to negated forms like "hasn't", "haven't", and does that also apply to HAVE TO, meaning "must"?
I know it's pronounced "haff to", but can it lose the H and be reduced to /hEf/ if it's not stressed?

At least around here, yes, it does under go such, and for that matter practically all grammar words will very readily use initial /h/ when not strongly stressed, especially if not at the start of an utterance.

That should be "lose initial /h/" above.

At least around here, [ɛ] may show up in such positions, as does more commonly [ɛ̞]. However, they reflect underlying /ɛ̯æ/, the reflex of historical /æ/, not /ɜ/, the reflex of historical /ɜ/, which would be realized as [ɜ̟]. That said, for your examples, I myself have:

I have a girlfriend - [ˈɛ̯æv], [ˈhɛ̯æv]
I have seen it - [v̥], [ˈɛ̞ː], [ˈɛ̞ːv̥], [ˈhɛ̞ː], [ˈhɛ̞ːv̥], [ˈhɛ̯æ], [ˈhɛ̯æv̥]
I haven't seen it for a while - [ˈɛ̯æːn], [ˈɛ̯ævn̩], [ˈɛ̯ævn̩ʔ], [ˈɛ̯ævn̩ʔt], [ˈhɛ̯æːn], [ˈhɛ̯ævn̩], [ˈhɛ̯ævn̩ʔ], [ˈhɛ̯ævn̩ʔt]
I don't have a car - [ˈɛ̯æv], [ˈhɛ̯æv]
She hasn't seen it - [ˈɛ̯æzn̩], [ˈɛ̯æzn̩ʔ], [ˈɛ̯æzn̩ʔt], [ˈhɛ̯æzn̩], [ˈhɛ̯æzn̩ʔ], [ˈhɛ̯æzn̩ʔt]
I have to check it - [ˈɛ̞ftʲə], [ˈɛ̞ftʲʉ̯̆ŭ], [ˈhɛ̞ftʲə], [ˈhɛ̞ftʲʉ̯̆ŭ], [ˈhɛ̯̆æ̆ftʲə], [ˈhɛ̯̆æ̆ftʲʉ̯̆ŭ]
He has to do it - [ˈɛ̞sʲtʲəː] [ˈɛ̞sʲtʲʉ̯u] [ˈhɛ̞sʲtʲəː] [ˈhɛ̞sʲtʲʉ̯u] [ˈhɛ̯̆æ̆sʲtʲəː] [ˈhɛ̯̆æ̆sʲtʲʉ̯u]

That should be "/ɜ/, the reflex of historical /ɛ/" above.

I see, thanks. I'll keep paying attention to weak forms, and if I have more questions, I'll be back. ;-)