"Come to nothing" is an idiom meaning be completely destroyed. This phrase expands on the word "fall" and emphasizes complete destruction. AT: "mountains completely fall apart" (See: [[rc://en/ta/man/translate/figs-doublet]])
If it is easier in your language, you can put this phrase at the beginning of verse 18 and adjust the text accordingly. AT: "You destroy the hope of man, just like ... dust of the earth" (See: [[rc://en/ta/man/translate/figs-simile]])
Destroying hope represents causing the things people hope for not to happen. AT: "You prevent the hope of man from happening" (See: [[rc://en/ta/man/translate/figs-metaphor]])
The abstract noun "hopes" can be expressed with the verb "hope." AT: "the things that man hopes for" (See: [[rc://en/ta/man/translate/figs-abstractnouns]])