As a wise man (or failing that, me) said (Nick Nicholas’ answer to Which language is older, Persian or Arabic?):
There’s no such thing as an older language.
Markus Zeeb brought up all the right caveats about Basque in his answer:
so Basque might be the oldest (or rather longest continuously spoken) language in Europe (whatever that means, to be honest).
And Aquitanian, the actual ancestor of Basque, prominently figures in my answer above.
So no, Wendish (Sorbian languages) may have been spoken in Eastern Germany before German was. But Wendish is not meaningfully older than German, and is no older than Slovakian, or Greek, or Spanish, or Aquitanian. Even if Wendish were extraordinarily conservative as an Indo-European language, which is not a claim I’ve heard.