some things you can do to save time are...

use charged shots with Phineas whenever you need to.

but Phineas is the slowest character so avoid using him whenever you can.

you should jump as less as you can. When you land you stop for a split second. Note this doesn't happen when falling from a ledge that is low to the ground.

When in the parts where you ride the dog, you shouldnt kill alot of enemies. It creates lag and slows you down.