Hi there,
You can use Joomla language override https://docs.joomla.org/J3.x:Language_Overrides_in_Joomla to translate the text. Here the list “Language Constant”
COM_QUIX_EMAIL_SENT_SUCCESSFUL
COM_QUIX_EMAIL_SENT_ERROR
QX_CF_YOUR_NAME
QX_CF_YOUR_EMAIL
QX_CF_YOUR_SUBJECT
QX_CF_YOUR_MESSAGE
QX_CF_SEND
QX_CF_YOUR_NAME_HINT
QX_CF_YOUR_EMAIL_HINT
QX_CF_YOUR_SUBJECT_HINT
QX_CF_YOUR_MESSAGE_HINT