"Negenentwintig is meer dan achtentwintig, achtentwintig is meer dan zevenentwintig, en zevenentwintig is meer dan zesentwintig."
Translation:Twenty-nine is more than twenty-eight, twenty-eight is more than twenty-seven, and twenty-seven is more than twenty-six.
I would think for Dutch to English, that should be OK - after all it shows that you know what the numbers are in Dutch, which is the goal here. But that's up to the course moderators.
This would be a bit much to type - in Dutch or English - on a mobile device without a keyboard.
No, in English you either write a number in numerals or spell it out - you don't go both ways. So you'd say either "twenty-nine" or "29."
For formal writing, by the way, you should consult the style book for your field or publication. Style books don't rule on what's correct; instead, they are there to establish consistency. So, for example, one style manual might say that you should always spell out the numbers from one to a hundred; another would have you spell out only the numbers from one to ten.