Need help with pronounciation, please help

I am a Chinese guy who have stayed in Australia for a few years, I can speak English pretty fluently now, but I still have a big confusion in pronouncing the letter "R" and "v", and also when pronouncing these letters in a word.

Here is how i pronounce them,
Basically, I just pronounce "R" as "W", for example:
"read", i will pronounce it as "weed",
"roll", i will pronounce it as "woll"
and it sounds pretty much the same. I know its incorrect, but does any of you pronounce the same way as I do? And whats the correct way to pronounce it?

I heard you need to roll your toungue a bit to touch the upper palate to pronounce it. I try it and I find its relatively easy to pronounce the first r in a word, such as read, red etc. But I find it hard to do the same when the letter r is in the middle of a word such as:
Reference do you still roll your tounge at the second r?
I usually just pronounce it as refence to be simple.

Also, to pronounce V or F in a word, do you tend to use the lower lip to touch the upper teeth to pronounce it, or just "intend" to blow it(mayb u touched ur teeth a bit, but wasn't intended). I usually just blow the "v" or "f" with lips touching nothing.Is this correct or acceptable?

You guys should be expert, since you are native speakers. Please teach me, your help is deeply appreciated.