Week 3 is done. Now test yourself!
How much of an improvement is enough to go to the next level? That's up to you. Maybe you're aiming for a 25% improvement, or maybe you want to be able to do 50 push-ups in 50 seconds. You're in charge. If you want to do the first three weeks again, go for it! If you want to move on to more challenging exercises, go on to Week 4. Nothing's stopping you. You can always switch back if you want to.