If you are an employee, you get sick pay (Krankengeld) when you are too sick to work. For the first 6 weeks, you are paid your full salary. After 6 weeks, you only get 70% of your salary.1
Krankengeld calculator (in German) – Techniker Krankenkasse
Krankengeld calculator – Arbeitnow
If you are a freelancer, you do not get Krankengeld unless you pay for it.2 By default, most freelancers do not pay for it. You can also get disability insurance (Berufsunfähigkeitsversicherung). It pays your salary if you are too sick or injured to work.