What is the contradiction they are talking about throughout the text? (response 5)

The contradiction I believe Marx and Engels are discussing throughout The German Ideology is that between the productive forces of labor and the form of intercourse. It is this contradiction that Marx blames for the upper class’s exploitation of the working class and the rise and inevitable fall of capitalism in Europe. It is my understanding that the productive forces refer to the combination of human labor and means of labor, such as machinery and tools, which lies in the hands of the worker. The form of intercourse is directly related to the division of labor that allows the upper class to control the worker and profit from him while destroying the system that sustains him. As the form of intercourse changes and the means of labor shift due to the greed of the upper class, the worker loses his place and livelihood. Marx says that this conflict has historically lead to revolution among the displaced and disgruntled working class and will continue to do sure, therefore ensuring that capitalism eventually fails. This contradiction is at its essences a conflict between the poor and rich, while the poor supply the labor, the rich control it and therefore there will never be harmony unless the distribution of labor is done equally.