"Is your name Omar?"
Translation:هَل اِسْمَك عُمَر؟
to be precise with vowels here, it should be: هَلْ اِسْمُكَ عُمَرْ (hal ismuka 3umar) - anyway we don't use the vowels markers (harakat) in our daily writing or typing most of the time. We just use them sometimes to emphasize something at some points to make sure the reader receives the meaning clearly (and that usage is dependent on the writer; some do like to and some simply don't care either)
Well, we have two words here: Hal (interrogative) and ismuka (your name) - I know, Duolingo says it differently vowel-wise because it's a wrong rendition from a machine.
Anyway, The word اسمك (ismuka) starts with what we call Hamzat-Wassl همزة وصل. This type of Alif acts like a schwa somehow and actually it gets annihilated by the vowel or the word preceding it. So, by listening, it might sound something like (halismuka). But it's important to keep in mind that they are two words and there is such a very brief pause between (hal) and (ismuka).