Thanks a bunch Scott, it worked like a charm.
I know have
line 212:
<legend> '.__('','cfiii').'</legend><div><em>* '.__('Required fields','cfiii').'</em>' . $wpcf_strings['error'] . '</div>
and line 222:
</form>');
for the moment, result can be seen at https://chouf.be/wordpress/?page_id=3 or later, at https://www.chouf.be
Thanks a million and happy xmas