How to convert virtual money into Gold?

In order to convert virtual money into Gold, or Gold into virtual money you have to access the menu  Bonus&VIP, and select the section Bonus Cards (the green cards).
In order to exchange virtual money in Gold you have to raise the 4th user level. Starting with this level you'll be able to convert  5 Gold per month (30 days). The amount of Gold that can be converted increases with 5 Gold when raising a level. In this way, according to the example below (the image) - at the user level 12 can be converted 45  Gold per month. The amount is NOT accumulated through the time. This means if you won't raise the level till 13, in the next month you'll be able to exchange the same amount  of 45  Gold - and it doesn't matter if you did or did not convert Gold in the previous month.
You can exchange Gold to virtual currency without limits. As we can see in the example I can change 1, 3 or 5 Gold for a certain amount of virtual money; or I can have 5 or 10 Gold in exchange to virtual currency.