Suki desu

[Peter_20]

俺はこの言葉がとても好きだから、マイニチ勉強すんだよ。

I learned them through memorization, obviously. I'm still having trouble with distinguishing 「シ」、「ン」、「ツ」、and 「ソ」, but it can't be helped.

I'd recommend practicing by writing them over and over again, in the proper stroke order (that's how I memorized them, anyway). That way you can tell katakana shi/tsu and n/so apart. Remember that katakana shi has the curvy line going up 「シ」, and tsu has it going down 「ツ」. Katakana n has it going up 「ン」, and so has it going down 「ソ」.

This is how I tell said Katakana letters apart:

シ and ン use more or less horizontal dots, and they are placed high up.
ツ and ソ use relatively vertical dots, and they're positioned further down.

I only know hiragana and some katakana. What's a good way to learn kanji? ;-;

First of all, make sure you get used to the radicals.
A radical is a component that serves as a "building block" for a Kanji.

Next, make sure you always actually memorize the radicals, NOT every single stroke.
For example, the Kanji for "demon", 魔 (ま), consists of 21 strokes, but if you know what you're doing, you can easily memorize it by memorizing 4 components!

And finally, you should focus on memorizing compounds rather than single Kanji.
You don't even need to know the meaning of certain Kanji, the only things that matter are if you know the compound and how to read it.
Besides, if you frequently study Kanji and learn new words, the meaning of each Kanji will become clearer and clearer anyway.
For example, take a look at these compounds:

洗車 (せんしゃ) = car wash
電車 (でんしゃ) = train
洗濯機 (せんたくき) = washing machine

If you compare these compounds, then I'm fairly sure you can guess the basic meaning of 車 and 洗.