How to say “It doesn’t matter” in Japanese?

気にしなくていいです / きにしなくていいです(kinisinakuteiidesu) = “Never mind”
気にしなくていい / きにしなくていい(kinisinakuteii) = “Never mind”

かまいません (kamaimasen) = “I don’t care”
かまわない (kamawanai) = “I don’t care”

1) 待たせてごめんなさい / またせてごめんなさい (matasete gomennasai)

Sorry for have kept you waiting.

matu = wait
mataseru = have keep you waiting
gomennasai = sorry

気にしなくていいです / きにしなくていいです (kinisinakuteiidesu)

It doesn’t matter.

2) あなたはお寿司と天ぷらのどちらを食べたいですか？ / あなたはおすしとてんぷらのどちらがたべたいですか？ (anata wa osushi to tempura no dotira o tabetaidesuka?)

Which do you want to eat, sushi or tempra?

anata = you
osushi = sushi
to = or
tempra = tempra
dotira = which
taberu = eat
sitai = want to
tabetai = want to eat you waiting

どちらでもかまいません (dotirademo kamaimasen)

It doesn’t matter which it is.

dotira = which
dotira demo = which it is
kamaimasen = it doesn’t matter