You can't just throw in correlative conjunctions wherever you want. They only work when connecting two parts of a sentence that are grammatically equal.
Example
Grammar is hard not only for English language learners, but also for native speakers.
OR
Grammar is hard not only for English language learners, but also because there are so many exceptions to the rule.
Oof. The second example is cringeworthy. "For English language learners" and "because there are so many exceptions to the rule" are not grammatically equal, so you can't use the not only/but also. Sorry, dudes.