[_ak]

They might be asking for things that they're not really eligible to know, or fishing for a pretext to get rid of him. Employment courts in Germany are very employee-friendly, and most cases (90+ %) are settled. Lawyer fees are strictly based on the value of the case (i.e. how much money/compensation the case is about), and each party has to pay for their own lawyer no matter what the verdict is (a rule to financially protect the more vulnerable employee from being financially ruined by the large corporation with expensive lawyers), so the financial risk for firing someone which is then eventually judged to have been done illegally is relatively limited and financially very predictable.

But the rules regarding long-term sickness are clear: the employee only has to send them the renewed sick notes, that's it.

[Mithaldu]

I think doktrin makes a better point, but this is information that is good to know too. I have edited the post above to point out that this stuff should be read too.