It's important for you to understand.

Every second counts.

We ran out of time. Now every second counts. / У нас закончилось время. Сейчас важна каждая секунда. (Каждая секунда на счету)

There's only one thing that matters now.

There's only one thing that matters.

That's all that's important.

для меня это очень важно перевод на английский

It's very important to me.

важно все сделать правильно перевод на английский

It's important to get it right.