Hey Lea, I'm a acrylic partner myself. You have done a really good job so far. I think your piece looks a lot cooler than the reference image. I think this is possibly due to you mixing white to lighten up a colour. This isn't necessarily bad. But in the reference image all the lights are yellow. What you can do to fix this, is to mix a yellow (preferably transparent) with a glazing medium and do some thin transparent layers over everything. This will lighten your darks, so you might want to mix burnt sienna and burnt umber with a glazing medium and paint the dark areas again. Try mixing 1 part colour, 2 parts medium and don't put too much on at a time, do thin coats. Don't worry they dry really quickly. You want to prevent high peaks when you are working with such transparent colours, cause those peaks will be more opaque. Anyway hope this helps, and look forward to seeing the results. Good luck

Yes, the lighting is off, but your reference is too dark to be useful. This is not really an acrylics issue...