I downloaded MW3 and ppatch it with the Download-Files to play it with 4D1...but it always say, that there is an Setam Connection Error??? How can I fix it?

Depends, which error do you mean ? There are more 'Steam' related errors.

Ok...Here:

 

"Error during initialization:

Steam must be running for initials authentication to success. Please

start Steam and reset the Game to continue"

 

Thats it... -.-

Run steam and make sure your steam profile is set to public

Run steam and make sure your steam profile is set to public

 

Were can I set it to "public" ??

Ok, now I have a new Error...if I run the game and the Menu is popping up, an Error appears and the Game closed...the Error means:

 

"ui_mp"

 

Thats it, not more or less, just "ui_mp" How can I fix this Error??

Go at your profile --> Edit your profile --> Settings