I'm planning to trip to Japan on September. = I'm planning to trip to Japan in September.
It's my second time to Japan. = It's my second time going to Japan.

It'll be still hot on September. = It'll still be hot in September.

So I'm worried about that.
But if I enjoy the shopping in Tokyo, It'll be okay. = But if I enjoy shopping in Tokyo, It'll be great.
I like to buy a Suntory whisky, instant cup ramens, cosmetics and a special salt for meat. = I would like to buy a Suntory whisky, a box of instant cup ramen, cosmetics, and a special salt for meat.
These are expensive or They don't sale these in Korea. = These are expensive or they don't sell in Korea./ or they are not available in Korea.

Great job, Misong. The same corrections on your previous homework, proper capitalization, usage of words, and prepositions.