Stay on your toes, and keep your weight above your feet; if you over-balance, you won’t be able to react quickly
Small steps are faster than big lunges
Move around where possible; a moving mark is harder to break
Focus on your footwork, moving sideways and then dropping back and forward again. Make sure you are balanced and in control of your movements as opposed to lunging and overbalancing. As you practice you will get stronger and faster.
You can use your body to limit space, experiment with how far across you can position yourself onto the shown throw and still make it across to cover the second option, it may be further than you think