A typical mistake in language education is harping on about linguistic correctness. This runs the risk of suffocating the joy of language. For the emphasis should be placed on the joy, and also the advantages, of acquiring an additional language, and not on the mistakes, which are part and parcel of language learning. If the child makes mistakes, do not make them explicitly aware of the error, because, by doing this, you will cause your child to lose his or her intrinsic motivation and joy of language. Instead, try to repeat the incorrectly pronounced word correctly in another sentence. Over time, your child will automatically revert to the correct pronunciation.
Likewise, there is sometimes a risk of falling too much into being overly correct. This is often the case when one tries to translate all words into their exactly corresponding counterparts in the language to be learned or one's own mother tongue. One often forgets that certain loan words have already become established in the dominant language. In such situations, it is important not to neglect the spirit of the times. Because it is of no use if the child knows the correct translation, but it is hardly used in everyday life.
Source: Cathomas, Rico und Carigiet, Werner. Top-Chance Mehrsprachigkeit. Zwei- und mehrsprachige Erziehung in Familie und Schule (2008, 1. Aufl.), p. 52.