Not in Welsh. It is more common in Welsh than in English to change the word order for emphasis - the thing being emphasised - rhan amser, here - is moved to the front of the sentence. This is more or less always done in 'identification' sentences, where the thing being emphasised is someone's name or occupation:
- Dewi yw hwnna - That's Dewi
- Mecanic yw e - He is a mechanic
- Arddwr ydw i - I'm a ploughman
And with other things being emphasised:
- Dim ond rhan amser mae e'n gweithio nawr - He just works part-time now.
- Yn Swyddfa'r Post mae hi'n gweithio nawr, nid yn y llyfrgell - She works in the Post Office now, not in the library.
One major dictionary shows it hyphenated, another has it unhyphenated. Either will do.
Can you add the hyphenated version as a correct option then? Also in other places in this lesson.