https://housinganywhere.com/Germany/mail-in-germany
https://www.howtogermany.com/pages/postal.html
Read and enjoy
For all the forward-looking plans, the old-fashioned delivery of letters and parcels still accounts for the majority of the Post's business. Even back in its bureaucratic days, the German post office had a reputation for speedy delivery, and the private company has further improved on it: 95% of letters are delivered within one day, and 99% within two days. Most packages can be delivered within a 400-kilometer radius in one day and nationwide within two days.