Do planets orbit around the sun at the same speed?

No. The farther away you get from the sun, the slower the planets orbit. (and the sun looks smaller!). By the way, even if the planets were all moving at the same speed, they still wouldn't be lined up, because the distances traveled by planets with each revolution around the sun would be different. Therefore this question is reasonable.

(this is another person)
they do orbit more slowly, Newton's law of universal gravitation states that the larger the mass of the two objects and the closer together the objects are, the greater the force of gravity between the two objects.