Could I get some feedback on my first normalisation design?
Community wiki answer:

A given athlete can play in multiple sports, so you should probably separate that. Also I do not understand the ranking part attached to countries. This should be at best a view, not a table.

As a general advice, do not store ages for individuals, but date of birth, because this does not change while the age changes each year.

You should just store the result (position) number for each athlete and competition, not medals that will be derived from it.

You also need to take into account ex-aequos. Also, even for a given competition, a given athlete may participate in multiple steps (semi-finals, final, etc.) so you may need to cater for that.