What price need choose ask, bid or last?
The ask price is the price that people want to sell it to you for. When you want to buy, you choose the ask price.
The bid price is the price that people are willing to pay for it. When you want to sell, you choose the bid price.
The last price is just the price that was used on the most recent trade.
It's important to note that you don't
have to stick with those ask and bid prices though - you can set whatever price you want, but you just have to hope that someone fills your order. That's why there is a gap between the ask and bid prices.
When I open sell order at last price, order is opened long time.. not instantly.
There could be two problems:
-The volume is too low in that trading pair for your order to be filled.
-You chose a different price than the bid price, so you have to hope that someone wants to fills your order
If you want your trade to be instant, take a look at the button that says "good 'til cancelled" and change it to "instant or cancel" so that the trade will be cancelled if it is not filled instantly.