[throwaway9283i]

Which are the "popular services" you are referring to? Can you elaborate?

In my current specific situation there are no coworkers from Germany.

I didn't even know that a US-based company can give me a German contract. Do you know the specifics how the stuff got deducted automatically (except the taxes)?

[heipei]

For taxes I use the online version of WiSo Steuer for example: https://www.steuer-web.de These services can pull your records on file from the tax office, so all you have to fill in is any additional items (deductible expenses over the year for example).

I don't know any of the details of how the company made the employment work. If you PM me I will give you the name of our German accounting firm which handled everything.