Erwin,
You are being too hard on yourself...I wish my first bust looked half as good as this...you picked a very difficult piece to cut your teeth on, and I think it's great...Lotsa folks here on the planet are more than willing to talk with you and help you along.
My greatest piece of advice came from Alan Ball, he told me to "look and see what works from many artist and then adapt their technique to yours..." Ask questions and am sure you'll get many folks helping you out.
I understand that you use oils for your fleshtones...you might want to consider using more of a flesh ochre for the base tone rather than the burnt sienna. The felsh ochre gives more of a consistent tone rather than a shade of orange...do you use oils exclusively?
Patrick