YOU SAID:

My sister is really annoying and I really don't understand why and that annoys me even more

INTO JAPANESE

私の妹は本当にうるさくて、なぜ私は本当に理解していません、そしてそれは私をさらにいらいらさせます

BACK INTO ENGLISH

My sister is really noisy, I don't really understand why, and it makes me even more annoyed

INTO JAPANESE

私の妹は本当にうるさいです、私は理由を本当に理解していません、そしてそれは私をさらにいらいらさせます

BACK INTO ENGLISH

My sister is really noisy, I don't really understand why, and it makes me even more annoyed