If you were on holiday and you lost your passport, would you know what to do? If you were on holiday and lost your passport, would you know what to do?

This was technically correct, but it sounds unwieldy. Something like my correction (which doesn't repeat the subject) or "If you lost your passport while on holiday" would sound better.

I think that if I lose my passport when I am abroad, I should try to find the aembassy of my country. I think that if I lose my passport when I am abroad, I should try to find the embassy of my country.

"That" as a conjunction is generally optional in English, so you could also omit it here. At times, that might sound more natural.

If I can´'t go to the aembassy, because the embassy is far for instance, I should try to phone to the aembassy. If I can't go to the embassy, because the embassy is far for instance, I should try to phone the embassy.

Unlike the French "téléphoner", "phone" takes a direct object.

If the embassy is not available, I should contact the police of the country I'm visit.ing. If the embassy is not available, I should contact the police of the country I'm visiting.