[Ideal Web Tech]

That looks right, however I would do it this way:

<vb:if condition="$post['field10'] == XXX">
	<vb:if condition="$timespentonline_formatted">
		<dt>{vb:rawphrase iwt_timespentonline}</dt> <dd>{vb:raw timespentonline_formatted}</dd>
	</vb:if>
	<vb:if condition="$timespentonlineperday_formatted">
		<dt>{vb:rawphrase iwt_timespentonline_average}</dt> <dd>{vb:raw timespentonlineperday_formatted}</dd>
	</vb:if>
</vb:if>

In which case it should be defaulted to either yes or no, but you can change the if to also show when only not no if you for some reason can't/don't want to default it.

And where XXX is you would put, "Ja", 1, true... or whatever your yes is stored in the database as... as per why your current one isn't working, all I can say is its probably not storing a "Nein" in the database but most likely a 1 or 0 (true or false).