this is one example how they are made in Kunena ,

but this functions is in almost  all forums.

I'll ask our developers in order to provide some tips for this case and I'll let you know as soon as possible.

Is there a way to make it custom ? Order it to you or some instructions to make it ourselfs ?

is very important because you can choose the forum that you want and the forums that you want to show.

For example maybe one forum is interesting discussion and the other only downloads where they post tones of posts and just  makes full the widget.

And other people were asking for it,

maybe you hadnt in your mind what we talk about and you didnt understood it.

Ok, I've understood your question now. I'm sorry, but there is no such a feature for wpForo widgets. 

If i want a new posts widget ,with the answers only from how to and troubleshooting category, or maybe i want a widget with all new posts BUT not from troubleshooting category.

Is it possible to do it ?

wpForo Widgets can be added in sidebars like other widgets. You can find wpForo widgets in Dashboard > Appearance > Widget admin page. 

More info here: https://wpforo.com/docs/root/getting-started/forum-sidebar-and-widgets/wpforo-widgets/