How to deal with a toddler (3years old) when I ask my kid to do something and the reply always goes "I think..." "Later ok?" Constantly negotiating with me to stall time.

haha.. I used to do that as a child. My mummy will go "why not now?" in response and kept rebutting my responses till I finally gave up and do the task. Kind of a battle of wills. I'm glad she won most of the time as I've learned that it is really not that torturous to do the tasks now rather than later. Plus! I get to enjoy the activities more after I've cleared the tasks. Just sharing! haha.. not sure if it will work for your child.