This question can only be answered for your individual case. If you are off sick with COVID-19, this may last a few weeks or several months depending on the severity of your illness. The long-term effects of the illness are also different in different cases and can affect your future working life to a greater or lesser extent.

Most of those who have had COVID-19 can go back to their old job after recovering from the illness. However, in some cases, long COVID reduces a person's ability to work and concentrate for longer periods of time.

In some cases, people who have been off sick for a longer period are able to ease back into work gradually, starting on a part-time basis and progressively increasing their hours (a graduated part-time working arrangement or Teilzeitregelung). If this is an option you would consider, you should ask your employer about it.
You may be entitled to a partial reduced working capacity pension (Teilerwerbsminderungsrente) which helps to make up for the loss of earnings due to part-time working. 

It may be that you caught COVID-19 because of your job, for example healthcare work in contact with infected people. If your COVID-19 is classed as an occupational illness (Berufskrankheit) you are entitled to special benefits. Further information about occupational illnesses is available here.

Medical or vocational rehabilitation can improve your physical capacity and help you to get back into working life after a period of illness. Further information about rehabilitation is available in the “Rehabilitation” section.

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