Examples if just in Czech examples

How do I translate if just into Czech?

Movie subtitles

Just go to sleep. If you don't want to die.

Spi, jestli nechceš zmrznout.

If she doesn't know, you can just keep telling her.

Jestli to nechápe, říkej jí to znovu a znovu.

News and current affairs

But if the human capacity for destruction knows few limits, the ability to start over again is just as remarkable.

Pokud je však lidská schopnost destrukce téměř bezbřehá, pak schopnost začínat znovu je neméně pozoruhodná.