Question about preposition of 'in'

Question

I'll show you two sentences concerning the preposition of 'in'.

1) I'm interested in traveling.

In this sentence, there seems to be two possible definitioins to me. First, taking part in something. Second, concerning something.

2)She kicked him in the stomach.

Also, I think that there are two possible definitions to me. First, concerning something. Second, at the point within an area or a space.

Source : https://www.oxfordlearnersdictionaries.com/definition/english/in_1?q=in

I'm not a native speaker as you know. There are many confusing definition in preposition to me. It seems to be mother-tongue problem. It is hard to get clear meaning of words and sentence concerning translation. Sometimes, some seems to be similar. I think that a little difference is very important. Is there anyone who let me know correct answer above sentences?

Answer 1

The word in is used in so many ways that the Oxford Learners' Dictionary can't cover all of them.

Interested in is a standard phrase for someone who is keen to take part in an activity or to learn about it.

In is often used with a part of the body when an action is applied to it, for example 'look him in the eyes,' 'poke him in the ribs' etc. Sometimes it's on - 'pat him on the back'. You just have to learn which preposition is used where.