Translation:In winter, children often have colds.
There are generally three places where you can place an adverb like "often" in a sentence in English when it applies to a whole sentence.
At the beginning: "Often, in winter, children have colds."
Before the main verb (so ignoring auxiliary verbs): "In winter, children often have colds."
At the end: "In winter, children have colds often."
This rule can vary depending on the specific adverb. Sometimes, one option can sound more or less natural than the others, to varying degrees. In this particular example, I would say that all three are perfectly acceptable, but the second option where "often" is in the middle sounds just slightly more natural than the other two options.