Hi Lucy!
⭐️ The two people are talking about physical exercise.
⭐️ In this context fit means: healthy, able to do exercise easily.
📚Examples:
⭐️ Lucy is very fit, she can run 5km in twenty minutes!
⭐️I couldn't run a marathon, I'm not fit enough! I would need to train a lot more to be ready.
⭐️If you are fit & healthy and love football, then join our team today!
❗️We can use the prefix un- to make it negative.
⭐️Oh my god, I'm so unfit. I need to rest for five minutes before we continue!
📌Extra:
⭐️ In the UK fit can also mean very attractive
📚EXAMPLE:
⭐️ Wow she is so fit! I wonder if she has a boyfriend?
⭐️He is so fit! It's a shame he has a horrible personality!