riverboats – Identify location (and painter) of old painting

The church tower on the second picture looks like Sankt Michaelis (Michel) in Hamburg. The tower is black nowadays but it was rebuilt several times in the last 150 years (especially it burned down in 1906) so depending on the year the painting was done it might have looked different (or the artist took the liberty to alter the reality a bit on it :-))

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Source https://en.wikipedia.org/wiki/File:Hamburg-Michaeliskirche-Hafen.jpg

The name of the artist seems to be “F. Müller”. Müller (Miller) is a very common name in Germany, so you might need an art specialist to find out details. Franz Müller-Gossen might fit but seems to have a different signature and a slightly different style, it also could be somebody who hasn’t left traces in the Internet.