1: Let's definition Hiragana and Katakana

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Hiranaga: This is pure alphabetical, simple, rounded Japanese symbols developed in Japan, used for writing the words belong to Japan.
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Simple, angular Japanese symbols derived from kanji in Japan. Used for writing people name, country name and often used to writing music name and the word borrowed of foreign language.
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I'll show you plus information:
Japanese has two types:
Japanese word and Transformation word from latin (Always use Katakana).
Example:
Hapi (ハピ) - Happy (Always use katakana because it's latin word)
Shiawasena (幸せな) - Happy (Always use Hiranaga because it's pure alphabetical)
Shiawase (幸せ) - Happiness (ALways use Hiranaga because it's pure alphabetical)
Example 2:
My name is: Kawakami Nyuu (カワカミ ニュウ), always use katakana for people name, do not use Hiragana (Although it has the same meaning)
2: Look closer: You can see that different !
Shi: シ tsu: ツ
As you can see, Shi straight line than tsu
So: ソ N: ン
As you can see: So have long and curved strokes than N and etc... >.<...
You have to pay attention and remember the exact shape of those words.
3: Sorry i don't get it..