I know this thread is written in dutch, but I'll have to switch to english to answer.
To make people go to forums, one of the first things would be to have them interested in the life of their own division first. Since being a "regular" in D.II, I have always tried to make people discuss about games, transfers, cup games, teams expectations and so on.
Season 16 had only 4 posts. Season 17 had 16, thanks to 2 great managers who since have left the division, unfortunately.
Season 18 was a hit with over 200 posts. That was great to log in and see different managers participating, and we made it to 100 posts last season despite me having much less time to write stuff.
What I wanted to highlight, is that if no one ever takes the charge of writing stuff mand make people read the forum, it is very unlikely that another one will do so, on the contrary starting something up will make otherwise unactive managers join the fray. I also do that. I used to check this forum every once and then, but seeing nothing I'm not participating either, and in the end I can spend an entire month without even having a look.
Of course language is an issue, I think we can write in both languages for those who can, otherwise everybody arounds here understands english.