You are sitting strightly upwards and that's good.
I think you should have longer stirrups. A bit, at least. And try to get your heels more down. If it hurts, you can practise and make your muscles there longer by exercises (putting your heels down on stairs, chair,...) And on the second picture I have a feeling you are a bit flying
Try to hold with your upper legs. I think you're not riding for lond time and I can assure you taht MY beginnings were much more terrible