You are looking at the HTML representation of the XML format.
HTML is good for debugging, but is unsuitable for application use.
Specify the format parameter to change the output format.
To see the non HTML representation of the XML format, set format=xml.
See the complete documentation, or API help for more information. 
<?xml version="1.0"?>
<api>
  <query>
    <blocks>
      <block id="5" user="Schüler gesperrt" by="Andrea Schellmann" timestamp="2020-03-22T16:15:08Z" expiry="infinity" reason="Ungebührliches Verhalten" nocreate="" autoblock="" />
      <block id="4" user="Deutschseminar Universität Augsburg TN1" by="Andrea Schellmann" timestamp="2019-06-23T14:18:33Z" expiry="infinity" reason="Benutzer nicht mehr aktiv" nocreate="" autoblock="" noemail="" />
      <block id="3" user="A.Burgermeister" by="Karl Kirst" timestamp="2014-12-23T06:18:03Z" expiry="infinity" reason="Schutz vor möglichem Missbrauch" nocreate="" autoblock="" />
      <block id="2" user="Simon Dang" by="Michael Schuster" timestamp="2014-10-14T09:02:47Z" expiry="infinity" reason="Passwort vergessen, neu angelegt unter Dang Simon" />
      <block id="1" user="Braun0308" by="A.Burgermeister" timestamp="2008-04-25T03:31:29Z" expiry="infinity" reason="Einstellen unsinniger Seiten: Unklar, wie er überhaupt in dieses Wiki kam" nocreate="" autoblock="" noemail="" allowusertalk="" />
    </blocks>
  </query>
</api>