My target journal asks for "How this fits in" and "Implications". What is the difference?

Every journal prefers a different format, and what they want is not always clear from the wording. I suggest you look through the last few issues, see how other authors wrote their How this fits in, and follow their angle.

You mentioned that your study is a descriptive analysis showing that resistance to certain antibiotics has risen a lot in recent years. How this fits in would say that, for clinical infections with certain bacteria, clinicians should no longer choose a particular antibiotic for empirical therapy. Implications would say that your study shows a certain antibiotic is no longer suitable for empirical therapy, and that future research could focus on the mechanism of resistance, to give direction to the development and choice of future antibiotics.

The feature of this kind of question is that beginners find the two sections very similar, while experienced researchers see the difference at a glance. It helps to ask an experienced researcher.

A similar case: beginners often think many sentences in the abstract, introduction and discussion can be copied and pasted between them. In fact, they cannot. Each of these parts says something different. Think and write from the principle that every section has its own purpose.