otvori.7z: Use this if you are treating the filename as a noun. Since "otvori" begins with a vowel sound (the letter 'o'), "an" is the correct indefinite article (e.g., "I received an otvori.7z file").
otvori.7z: Use this if you are referring to a specific instance of that file (e.g., "Please extract the otvori.7z archive"). otvori.7z
In Croatian or Serbian (the languages where "otvori" means "open"), there are no indefinite articles, but the word is grammatically because of its "-i" or "-o" ending sounds, though filenames are often treated as masculine in casual technical speech. otvori