This poem is not so much difficult to understand as it is difficult to read because of its subject matter. Celan uses a lot of symbols, but they are usually easy to pick out (milk, vipers, etc.). Also, he writes in a disjointed style, in which phrases that don't seem to be related are put next to each other. Don't worry – this style is supposed to be disorienting, it's part of the effect of the poem. Finally, we try to explain some of the literary and cultural allusions in the poem in "Symbols, Imagery, and Wordplay," so you might find that helpful. Once you figure out who Marguerite and Shulamith are, you're set.