I am struggling to translate this xml file:

<document>
<metadata_list>
<metadata status="translating" type="doc_title">Document to translate</metadata>
</metadata_list>
<content>
<para id="para151374285">
<para_content lang="de-DE" status="translating">Título</para_content>
</para>
<para align="justify" id="para667863099">
<para_content lang="de-DE" status="translating">traducción a mano</para_content>
</para>
<para align="justify" id="para224593780">
<para_content lang="de-DE"/>
</para>
<para id="titleimage145389846">
<para_content lang="de-DE" status="translating">Imágen de ejemplo</para_content>
</para>
<para id="para650497377">
<para_content lang="de-DE" status="translating">1</para_content>
</para>
<para id="para252996714">
<para_content lang="de-DE" status="translating">uno</para_content>
</para>
<para id="para264174280">
<para_content lang="de-DE" status="translating">2</para_content>
</para>
<para id="para159549621">
<para_content lang="de-DE" status="translating">dos</para_content>
</para>
<para id="para751025178">
<para_content lang="de-DE" status="translating">3</para_content>
</para>
<para id="para733768577">
<para_content lang="de-DE" status="translating">tres</para_content>
</para>
<para align="justify" id="para734026856">
<para_content lang="de-DE"/>
</para>
<para align="justify" id="para516785049">
<para_content lang="de-DE" status="translating">Traducción de párrafo</para_content>
</para>
<para align="justify" id="para581804402">
<para_content lang="de-DE" status="translating">Traducción de párrafo</para_content>
</para>
<para align="justify" id="para182264526" modified="5">
<para_content lang="de-DE"/>
</para>
<para id="titleimage272840667" modified="5">
<para_content lang="de-DE" status="translating">imágen de prueba</para_content>
</para>
<para align="justify" id="para979668678" modified="5">
<para_content lang="de-DE"/>
</para>
<para align="justify" id="para127940730">
<para_content lang="de-DE" status="translating">Traducción de párrafo</para_content>
</para>
<para align="justify" id="para750127719">
<para_content lang="de-DE" status="translating">Traducción de párrafo</para_content>
</para>
</content>
</document>

The translation tool I use keeps telling me that “The file does not have any valid segments. If you are using a custom-made XML, please consider using XLIFF 1.2 instead”. Then they recommend “writing a piece of software that converts the xml file into XLIFF 1.2 and then vice versa”. I am learning to code, but I am not so advanced. Can someone help me about the necessary steps to do it? Thank you in advance.