そんなに遅くまで外出していてはいけません。

You mustn't stay out that late.

そんなに遅(おそ)くまで外出(がいしゅつ)していてはいけません。

Sonnani osoku made gaishutsushiteite waikemasen.

そんなに (そんなに)

so much; so; like that

遅い (おそい)

slow; late (e.g. "late at night"); too late; dull; stupid

迄 (まで)

until (a time); till; to; up to; to (a place); as far as; to (an extent); up to; so far as; even; only; merely

外出 (がいしゅつ、そとで)

outing; trip; going out

ば (ば)

if ... then; when; and; why don't you...?; the more (one does something); because; since

Readings: チ、おく.れる、おく.らす、おそ.い

Meanings: slow, late, back, later

Readings: ガイ、ゲ、そと、ほか、はず.す、はず.れる、と-

Meaning: outside

Readings: シュツ、スイ、で.る、 -で、だ.す、 -だ.す、い.でる、い.だす

Meanings: exit, leave, go out, come out, put out, protrude