"The employee has gimbap."
Translation:회사원이 김밥을 가지고 있어요.
가지다 (sometimes written as 갖다) means "to possess." This is hard to translate from English in most languages really. We just use "have" liberally.
That said, you can write this in 2 ways. You're probably thinking of this way:
회사원은 김밥이 있어요 - This means the same thing
When you use 가지다 (or 갖다), the particle changes to a direct object -> 김밥을
The difference between 가져요 and 가지고 있어요, I think, is that the former is an action word while the latter is a condition verb, meaning that 가져요 would not mean to "to (already) possess" but rather "to come into possession." If you say to someone "Here, take this" you would say in Korean "가져요." 가지고 있어요 can only be something that you already have.
If I'm wrong, please correct me mods.
If this is the case, the translation for this verb is wrong because there is another sentence that uses 가져요 to translate "the fox has the mouse." In which case, that sentence should be stative (has), and this one should translate as a continuous verb (is carrying) in English.