Translation:I wake up at eight thirty A.M.
No, don't be worried ;) Duo's "correction" is nonsensical and your answer is very natural. (Native Australian speaker here)
I will just say though, that I would accept your answer for general translation purposes, but for this learning exercise, I would consider it incorrect. 午前 translates more closely to "a.m." and I think it's better to learn 朝 (あさ) for "morning".
おきます is the ます form. Original form is おきる, better known as the dictionary form
The 6 commonly used conjugation forms are
ない, ます, dictionary, ば form, て form, た form
おきない dont wakeup
おきます wakeup - ます form
おきる wakeup - non polite dictionary
おきれば conditional ば form
おきて used to connect or form compound sentences
おきた past tense - non polite
Because each kanji may have many different pronunciations depending on which other kanji it is paired with.
The 前 part of 午前(ごぜん - A.M.) also is part of 名前 (なまえ - name).
I can't explain exactly why 牛 shows up as うま but you might find it interesting that 牛 on its own means cow (うし) and 牛馬 (うしうま) means butter.