Learn Hardcore Ukrainian: Поїздка була корисною, бо я міг подумати про важливі речі. - The trip was useful because I could think about important things.

була is the past‐tense form of бути (“to be”). In Ukrainian, a copula is required in past and future tenses, so you cannot drop it here. In the present tense you can omit бути (e.g. Поїздка корисна), but in the past you need була.

Why is корисною in the instrumental case instead of the nominative?

When an adjective follows бути in a non‐present tense, it takes the instrumental case to link subject and predicate. Поїздка is feminine singular, so корисною is the feminine singular instrumental form (ending in -ою).

What’s the difference between бо and тому що, both meaning “because”?

бо is a short, colloquial conjunction meaning “because/for” and does not take що after it. тому що is the more explicit “because that” and always appears together. You can say …корисною, бо я міг… or …корисною, тому що я міг…, but never бо що.

Why is the verb phrase міг подумати used instead of міг думати?

Ukrainian contrasts imperfective (думати, “to be thinking”) with perfective (подумати, “to think (to completion)”). After могти (“could”), if you mean you had the opportunity to complete the act of thinking, you use the perfective подумати.

Which case follows the preposition про, and why are важливі речі unchanged?

про (“about”) governs the accusative case. речі is an inanimate feminine plural noun whose accusative plural equals its nominative plural (речі). The adjective важливі likewise uses the accusative plural, identical to the nominative form.

Can you drop the pronoun я in я міг подумати?

Yes. Ukrainian is a pro‐drop language, so міг подумати про важливі речі is perfectly fine and still means “I could think about important things.” The pronoun я is optional and adds emphasis or clarity.