i´m no dutchman, but a member of the north-frisian-clan in germany, they have the same roots like the east-frisian (they live south-west of us, there is the opinion, that they are the stupidest people in germany, don´t even know in which direction the live ;-) ) and the west-frisian in the netherlands.
so i think, i know i little of the mentality.
In my point of view, they are just not as open as what I thought compared to americans I know
one main part in the character of mostly all nothern europian peoples is
to speak nothing, if there is nothing to talk about. this could be interpreted as "not so open".
the contrast is to speak all the time even if you say nothing like the italians do. they also do it only in their own language and you have to learn it or have to learn how to use your hands.
if you prefer people that can talk in english go to sweden.
mostly all off them will understand you.
or try to get in contact with the guys of the nigeria connection, they are understanding a little of your language and seam to live in amsterdam.