Question

Have a good week! Postmodernism claims that there is no truth, since the meaning of truth is correspondence to reality, and we do not observe concepts themselves; therefore this is only a statement about the subject’s consciousness.
And it’s difficult for me:
A. What is new about this? After all, this is what follows from David Hume, who said that it is impossible to observe concepts and values, and if so then it would seem to follow that truth does not say anything about reality. Is the distinction that for Hume this at least says something about the subject, whereas for postmodernism it does not even do that?
B. What is the innovation of postmodernism compared to Marx? After all, he too said that what generates ideas is material desire. Is the distinction that for Marx one can still speak about concepts such as man and woman as truths grounded in nature, and only religion and the like are products of material desire, whereas for postmodernism one cannot make any induction at all regarding concepts and definitions?
Thank you very much!