Karl Marx and Friedrich Engels

"These various conditions, which appear first as conditions of self-activity, later as fetters upon it, form in the whole evolution of history a coherent series of forms of intercourse, the coherence of which consists in this: that in the place of an earlier form of intercourse, which has become a fetter, a new one is put, corresponding to the more developed productive forces and, hence, to the advanced mode of the self-activity of individuals- a form which in its turn becomes a fetter and is then replaced by another. Since these conditions correspond at every stage to the simultaneous development of the productive forces, their history is at the same time the history of the evolving productive forces taken over by each new generation, and is therefore the history of the development of the forces of the individuals themselves". (p. 19-20, last paragraph on p. 19)

I honestly had to reread this passage 2 times and I still did not understand what is going on in this passage. I really have no idea what Marx is saying here. In my opinion it feels as if each sentence in this passage is followed by what's supposed to be a beginning to a new sentence. It just really makes no type of sense to me, I feel like this whole reading is just saying "blah" to me.