彼はとても速く歩いたので、私はついていけなかった。

He walked so fast this I couldn't keep up with him.

彼(かれ)はとても速(はや)く歩(ある)いたので、私(わたし)はついていけなかった。

Kare wa totemo hayaku aruita node, watashi wa tsuiteikenakatta.

彼 (かれ)

he; him; his; boyfriend

は (は)

topic marker particle; indicates contrast with another option (stated or unstated); adds emphasis

迚も (とても、とっても)

very; awfully; exceedingly; (not) at all; by no means; simply (cannot)

早い (はやい)

fast; quick; hasty; brisk; early (in the day, etc.); premature; (too) soon; not yet; (too) early; easy; simple; quick

歩く (あるく)

to walk

ので (ので、んで)

that being the case; because of ...; the reason is ....; given that...

私 (わたし、わたくし)

I; me; private affairs; personal matter; secrecy; selfishness

付いて行ける (ついていける)

to follow; to keep in pace with; to understand

Readings: ヒ、かれ、かの、か.の

Meanings: he, that, the

Readings: ソク、はや.い、はや-、はや.める、すみ.やか

Meanings: quick, fast

Readings: ホ、ブ、フ、ある.く、あゆ.む

Meanings: walk, counter for steps

Readings: シ、わたくし、わたし

Meanings: private, I, me