I did my PhD part time while working full time in another country and I am not a native English speaker!
I did my PhD In sociology in the UK while living and working in special needs education in Greece...
It took me 7 years of hard work
The only advice I can give is having a programme and stick to it! I was working 6 hours a day on my job, then rest for an hour and then start working on my research for 3 hours every day. Then exercise a little bit every day. Also I was not working on weekends, except the odd one here and there.
If I managed to do it, then everybody can!