Kara (or dakara/desukara for nouns/na-adjectives) means "B happened because A happened". Node (or nanode for nouns/na-adjectives means) "A happened, therefore B happened". It is a bit softer, more polite and has more of an explanatory tone. I don't think "ga" means "because". When used after an adjective, noun or verb in a sentence it means "but" or "however". It doesn't necessarily have to have the same meaning as the English "but" though, it can also be used to simply connect sentences. I don't think "de" means "because" either. The only "de" I can think of is the "de" used when describing someone/something with several adjectives. You put a "de" after the na-adjectives/describing nouns and remove the last i and add kute for i-adjectives, except for the last adjective. Genkina hito desu. Yasashii hito desu. -> Genkide yasashii hito desu. Yasashikute, genkina hito desu.