A person who likes fishing. (낚시를 좋아하는 사람)

I happened to meet someone at work yesterday who likes fishing very much. at work yesterday.

Putting "at work yesterday" at the end works as well, but this clarifies a bit better.

He showed me pictures of when he caught some big fish.

"Fish" is a weird word where technically you can say "Fishes" as a plural form, but typically (in America) you'll hear people say "Fish" for both singular and plural form.

I asked him that where is a good place would to catch big fish.

Fishing is fun. I've been also had fishing xperiencese a few times in the past.

I asked him that where is a good place would catch big fishes is.

He said to told me that is it was a secret.

"say" when you only have a direct object. The direct object will be what you are quoting.

He said, "I am tired."
He said he was tired.

Here, "I am tired/he was tired" are the direct objects, but there is no indirect object.

"told" is used when you have a direct object (what you are quoting) and an indirect object (the person you are talking to about it).

He told me he was tired.

Here, "me is the indirect object, and "he was tired" is the direct object.

I asked him that where is a would be a good place would to catch big fishes.

He said to told me that it's a secret.