Easy question, very difficult to answer.
Yes and no. It depends what you are willing to do.
If you want to make totally new maps from scratch, means complete new landscapes etc.
you have to wait until hdmaster has finished his 3ds Max Plugin. For more information
follow this topic
.
But if you want to add soldiers, tanks or whatever on a existing map (e.g Africa 1) i would suggest to use RevEngEd 2
Editor by Ikaros which you can
download here
and for more information visit his
website
or
follow this topic
.
The DCED2 Editor is made for Mafia 1 but because of the same game engine you can use it for HaD2 as well accepting some bugs.
About handling these bugs i recommend
Hawk's DCED2 Tutorial
.
Like i said at the beginning, it depends strongly on what you want to do.
Adding just a simple tank in a existing map is relativly simple.
Create a new coop mod is already very difficult (scripting, placing objects and definitions, ...), especially for you, as all tutorials are in english language.
I would be really happy if you could overcome all the problems you will face. Don't give up please. We need more modders
If you have more detailed questions i would be glad to help. First i would say read through all the tutorials by Hawk & Zdenda. That's always a good start.