I knew that flood causelearned about a flood in America by watching the news in the middle ofwhile going to high school. I learned about a flood in America by watching the news while going to high school.

This response seems a little more natural in a conversation rather than saying "I knew" "In the middle of" is a preposition of where something could be but you're talking about it in a time sense, so you use words like while or during.

I klearnewd that floods were caused in America by watching news in the middle of going to high school. I learned that floods were caused in America by watching news in the middle of going to high school.

I am good at math, so itI was surprised for me tothat I missed a math problem. I am good at math, so I was surprised that I missed a math problem.

If you want to use it, you can say, "it was surprising to me", but if you want to use surprised, you have to use "I was surprised"

Also, I am good at math, so it was surpriseding for me to missget a math problem incorrect. Also, I am good at math, so it was surprising for me to get a math problem incorrect.

You switch topics abruptly here without acknowledging that you're doing it or giving context for when/where this event happened. I'd add another sentence at the start, like 'Also, in high school today, I got a math problem wrong.'

By the way, I haveam worriesd about my friends. By the way, I am worried about my friends.

You don't typically say you have worries, you use the verb to be, so are/am.

By the way, I have worries about my friends. By the way, I have worries about my friend.

Even though hwe shas myre a hobby, I think that his chat is boringhe's boring to talk to. Even though we share a hobby, he's boring to talk to.

Instead of he has my hobby, you say we share it because you both have it.

Even though hwe shas myre a hobby, I think that his chate is boring to talk to. Even though we share a hobby, I think that he is boring to talk to.

In addition, I'm get ready for Culture Festival. In addition, I'm get ready for Culture Festival.

In this one, you also use the verb to be, so you would say "I am getting ready..."

In addition, I getam getting ready for the Culture Festival. In addition, I am getting ready for the Culture Festival.

I'd add 'my high school's culture festival' to give more context.