What does this mean in English if you translate it? And what does this mean in pinyin, please tell me its very important!
I would translate it as
fantasy romance. The translation, as Farnz said, depends on the story. 梦幻 literally means like a dream. So it can be good (dream come true) or bad (empty dream).
The one thing that is certain is that it's something you don't expect to experience in normal daily life (can be supernatural, or just too many extreme coincidences happen in the story)
If you are talking about the online computer game 梦幻情缘, then fantasy romance would be perfect.
This Korean TV series https://en.wikipedia.org/wiki/Couple_or_Trouble is translated as 梦幻情侣 in Chinese and Fantasy couple in English. And you can take a look at its plot to get some context.
情缘：情通常指男女爱情，缘是缘分(the fate, the lot, the second cause)。
'梦幻' also means '美好的'(extraordinary, too good to be true)。
For example: 梦幻音乐。 It means wonderful music instead of fake music.
So, it depends on the whole story.
'梦幻情缘' may be a beautiful love when the story is real and good.