Exercise: Let your hand learn the lines.
When sketching, the hand learns the lines.
Sounds weird, but it’s a fact that drawing every day, improves the drawing skills of the hand. It's because of the muscle memory effect.
Your eyes look at the photo of the animal, the hand follows the impressions of the eyes. So this exercise has a double effect: you learn to see the main characteristics of the animal and at the same time you learn to follow those characteristic lines on the paper with your hand.
No line needs to be perfect.
Just draw it and feel this drawing in your hand.
That’s all what you need to learn drawing.
Don’t focus on this one and only perfect line – this line only happens, if you don’t focus on it.