I have the same confusion. I have started using Gtranslate on a separate tab to check words and small phrases. When doing these lesson I learned the треба is translated as "need" but Gt says that it means "should" and that потрібну is need as in "I need to buy paint"
I have heard it said that English is the most confusing language to learn, I guess they have never tried Ukrainian.
Well, ‘треба’ is a more colloquial variant of ‘потрібно’. And it's the most universal thing of all. You can use it for ‘need to’, ‘have to’, ‘must’ as well as for ‘should’ if you don't care about specifying what's the reason behind it. If you want to be precise on expressing modality then it's more or less like this:
- I need to inf — Мені треба/потрібно inf (Subject in Dative) — most usually when you have your own need.
- I should inf — Мені слід/варто/треба inf (Subject in Dative) — when it's for your own good / Я маю inf — a strong advice or a nonstrict order.
- I must inf — Я мушу/маю inf (Subj in Nominative, verb changes by person) — it may be not what you want but you must.
- I have to inf — Я маю inf (it's literally ‘I have to’) — similar to ‘must’. ‘Я мушу’ is slightly more about being forced to do so than ‘я маю’.
But it also depends on context, I must admit.
You're welcome. ‘I have to inf’ (as well as ‘must’) may have another translation: ‘Я повинен/повинний inf’ (повинен is an adjective, so it changes by Subject's gender and number). It means something like ‘There's no way I can avoid doing it’ — because it's either a strong need or an order, or a duty, or an ought. ‘Я повинен купити їжу’ — I have to buy some food (Nobody else does it and we all die.) Please compare it to ‘Я маю купити їжу’ which simply states that you have to buy it.
If you stress that you are forced by your circumstances to do something against your will then you say ‘Я змушений inf ’ (змушений is also an adjective.) ‘Я змушений тебе вбити’ — I have to kill you (Or else you will kill me.) It relates to ‘Я мушу’ as you may guess, but it expresses that you are forced into doing undesired things in a much clearer way.
Hope this helps as well :)