The answer, like most things in writing, is that it depends.
In my own poetry writing I've found that I am greatly helped by first learning and strictly following all stylistic guidelines. I have often been drawn towards formal verse structures such as the villanelle, Shakespearian-style sonnet, or sestina. By forcing myself to follow these guidelines, I really challenge my own creative process. I also learn what the rules do to the poem. I learn the impact of, say, repeating the same line at the end of every other stanza or how a certain rhythm and rhyme scheme hits the ear.
The really famous uses of all of these formal structures for poetry usually, although not always, end up breaking the rules or at least bending them. The key is that there is a structure to be twisted, and in knowing what the impact of that structure is and how twisting it in certain ways has certain impacts. For example if the poem is in iambic pentameter and there is an additional syllable on the line to make it longer or the stress falls on two syllables back to back, the reader will notice that line or those syllables more than other parts of the poem which might be comfortable.
One way of breaking the rules that novice poets often fall into and shouldn't is using antiquated language or awkward language constructs because "that's the way poetry is written." Actually, it is not. A poem by John Donne reads the way that it does because John Donne was writing somewhat in the vernacular of his time but also in a time before the English language was as standardized as it is now. The modern poetry-reading public does not tend to have a high tolerance for poetic license with grammatical constructs unless it really has a great, positive impact on your poem. You can't just re-structure sentences to fit a rhyme scheme and call it good poetry - you have to fit the rhyme scheme in a way that serves the grammar of your sentence, too.
The most revered modern poets often (not always) write very compressed language that also seems modern and moves smoothly. When they break these patterns, the impact adds to the theme and feel of the poem, it is not capricious. As a poet you'll have to learn how to do this as well.
I'd suggest reading some current German poets to get an idea of what's being done in the field and learning what impact different structures have.