3 year old never listening

We have a 3 year old and a 1 year old.

Our 3 year old does not listen to us and I’m at my wits end.

When it comes time to getting dressed, changing a diaper (we are still working on potty training), putting toys away, telling him no to candy (my husband always buys candy and I hate how much our kid eats of it, yet I’m a no fun mom if I tell him no to it all the time), nap or bedtime it’s just a hassle.

He’s all about telling us no, hitting or kicking right now. Basically we tell him not to do some and he does it anyways.

Does anyone have anything to help with this? Advice? Anything?