I have this:
http://www.coopers.com.au/the-brewers-guild/how-to-brew/ale/wheat-beer
And this (the wheat one)
http://www.coopers.com.au/the-brewers-guild/brewing-products/brew-sugars/malt-extract-range
Is that enough?
I have some light Malta extract, shall I add 0,5kg of this also?
As beginner I know I have to read more on the differences between the malta extracts
Basically you can mix/match extracts of the same grain however you want, because functionally there's no difference between Liquid malt extract and Dry malt extract except that DME is 20% more concentrated so .8kg DME gives you the same amount of sugars 1kg LME.
When planning a beer, you need to decide what your total grain budget will be.
Your budget will determine if your beer is "heavier" with more flavor or
lighter" and more refreshing.
For most brews you want your grain "budget" to be anywhere between 3.0kg of sugars and 5.0kg for a 5gallon/20liter batch.
The way your kit comes as I understand it puts your total fermentables at 3.3kg with 2.3kg of malt, and 1.0kg of dextrose.
As I explained in my previous post, dextrose ferments completely so it doesn't add any flavor, leaving you with only 2.3kg of malt to give your beer body and flavor. That is really really light. Not necessarily "bad", but very, very light.
Personally I'd either substitute that 1kg of dextrose with malt extract or simply use both if I wanted a higher ABV, you'll have more flavor and body with the extra extract, and to most people's tastes it'll probably taste better.
For the poster who said it was "too sweet" he probably used
malto-dextrine which does not ferment at all. I looked at the coopers site and they're pushing it pretty hard. The other way his beer would be too sweet is that he didn't let fermentation run long enough for the yeast to eat the extra sugar.
Brewing in general isn't a set of hard and fast rules, it's more of a spectrum that you adjust according to taste.
Are you doing a regular hop boil or are you using the pre-hopped extract stuff? I've never used pre-hopped extract so I cant quote exact numbers at you, but take into consideration that you need to use enough to get your desired bitterness.