How to sell all steam cards "fast"?

Only if you trase them with someone, if you want to sell them in marketplaxe you need to click one by one

Steam Economy Enhancer - free user script that can sell all your cards automatically. It searches best price by itself, it also can relist items that already are on the marketplace

1) trade with somebody
2) you can use some plugin , was it Enhanced Steam, or sth like that?

on each badge page on top there is a button "Sell these cards on the Market"
click it and it will navigate to another page where you can place your sell order (prices are already filled according to buy orders)
it is faster than one by one

I personally use Augmented Steam browser add-on. It's fast & easy. But I haven't done any research whether it's safe to use or not.

Very Nice!

I recently did the same, netted about $6

steamlvlup.com