well i tried to install the sdk and download it and it worked fine but then i come into that i can chose some games but there are only half life and counter strike how to add dark messiah there? i saw another topic where there were a link but nothing usefull so much to read but nothing usefull at all! i pressed anything i dont really know and there came a window where i could add a game but i cant find it now but i tryed it out and then i come where i have to put a file in with the end it should have the name for: css: /cstrike , halflife : HL2 and so on but i could not find the dark messiah one so plz help and dont send a stupid link with no usefull information

Search for SDK.doc in your Steam folder
You only have to follow the instructions...

i did but maybe im stupid then i simply dont understand the doc.. :P

No offence, but..
the infos on the doc are nothing compared to the darn grey Hammer window giving errors when compiling...
But you can always fill some fori with questions...
anyway:
First of all you must dload the Source SDK in Steam and launch it at least once;

Close Source SDK;

in the \sourcesdk\bin folder you have a file named GameConfig.txt (disable "hide files extentions" or similar statement in Control Panel\Folder Option)
Open gameconfig.txt with notepad or better ConText (google it), you'll find a lot of strings the last of those strings states:""SDKVersion" "2";

BEFORE this string add the content in the grey window at page 4 of SDK.pdf;

Add what indicates page 5 in gameinfo.txt in DM folder as stated;

go to Nem's page and dload GCFScape;

with it you can extract materials, models and surfaceproperties_arkane.txt files from the .gcf files in DMM&M MP folder.
Put them all as stated in the doc.

That's it launch SourceSDK select DM in "Current Game" on bottom, launch hammer and enjoy it.

Set Valve Developer Community page among "Favorites" and do not ask anything before reading it

first of all thx for help i will try that you wrote

you wellcome.
another usefull web site is 3D Buzz with some good video tutorial about HL2 Editing.