On Duolingo, I was asked to construct the sentence, "Dad always has questions." The correct answer was "У папы всегда есть вопросы." I got it wrong since I left out есть but I was wondering if this would be wrong 100% of the time or not. Like let's say I'm annoyed that he's always asking questions. Or... if there's any other way to construct that same sentence. It's said that Russian has less structure than other languages overall, but thus far Duolingo's sentences are pretty structured. Any advice/examples on flexibility to feed my curiosity? Thanks!
In the majority of cases it's actually not wrong to omit word "есть" and your particular example it is indeed completely acceptable to say just "У папы всегда вопросы".
In Russian whenever you can use "есть" (in sense to have) / "имеется" + noun you can omit this verb for affirmation. Examples:
У меня есть билет на концерт/
у меня билет на концерт
Там есть еда/
It's getting more complicated for questions:
Там еда? is acceptable but
есть там еда? is used more often.
Also, if affirmative sentence starts with
есть it can not be omitted. One can not just say
что выпить? instead of
есть что выпить?.
This is intentionally simplified, there are some constructions that de-facto are used more often with
есть than without it, but I believe this is enough for understanding basic usage.
Also it worth to mention that sometimes this
есть is used for emotional amplification, some in some context
у меня вопрос can sound like
I have a question and
у меня есть вопрос is something like
I do have a question.
I would say that when you use the word есть it underlines that he can have questions or reservations or doubts while not necessarily expressing them. He can keep the questions to himself for a time. On the other hand, without есть it more implies he asks the questions (not keeping to himself).
У меня есть вопросы по поводу нового оборудования = I have reservations/doubts/questions about the new equipment (not necessary want to share them).
У меня вопросы по поводу нового оборудования = I want to ask questions about the new equipment.