1.  I suppose this singer is very rich. If she (be) a poor woman she (not stay) at the Waldorf Astoria.

I suppose this singer is very rich. If she WERE / WAS a poor woman she WOULDN'T BE STAYING / WOULDN'T STAY at the Waldorf Astoria. 

2.  If I (see) a lion walking across this botanical garden I (climb) a tree. But I guess that (not be) useful because the lion (climb) after me.

If I SAW a lion walking across this botanical garden I WOULD CLIMB a tree. But I guess that WOULD NOT (WOULDN'T) BE useful because the lion WOULD CLIMB after me. 

3.  If my girlfriend (throw) her old clothes away she (have) to ask me for 2,000 dollars to buy new ones.

If my girlfriend THREW her old clothes away she WOULD HAVE to ask me for 2,000 dollars to buy new ones.

4.  A: If I (have) lots of money I (drink) French champagne with every dinner.
     B: If you (drink) champagne with every dinner you soon (get) tired of it.

A: If I HAD lots of money I WOULD DRINK French champagne with every dinner. B: If you DRANK champagne with every dinner you WOULD soon GET tired of it.

5.  Where you (go) if you (do) want to buy an elephant?

Where WOULD you GO if you DID want to buy an elephant?