Hi nicolas,
thanks for the tip.
For others how want to now:
I add from the registration.php the lins 40 to 43 e.g. the USERNAME
<label id="usernamemsg" for="register_username">
<?php echo JText::_( 'HIKA_USERNAME' ); ?>
</label>
to:
<label id="jform_username-lbl" class="hasTooltip required" title=""
for="register_username" data-original-title="
<strong><?php echo JText::_( 'HIKA_USERNAME' ); ?></strong><br />
<?php echo JText::_( 'COM_USERS_DESIRED_USERNAME' ); ?>">
<?php echo JText::_( 'HIKA_USERNAME' ); ?>
</label>