Qual è la differenza tra fling e affair ?Sentiti libero di rispondere con un esempio.

I think that you will find that opinions differ about the difference in meaning. For example,
1. Fling could be interpreted as both people involved are unattached whereas affair indicates one or other party has someone else
2. Fling could be used for something purely sexual whereas affair implies emotional attachment.
3. Fling could be used to describe a one-off whereas affair indicates longer duration
4. Fling is less formal than affair

There may be other differences that people would highlight but native speakers won’t use a consistent distinction so they are quasi synonyms in my view.