Having reached Green belt, more is expected of your Saifa ability. Therefore it’s important to practise regularly at home (and even before and/or after class). Your overall ability must have improved in the kata, and your instructor with have less tolerance of bad habits or neglect in the finer details.
Therefore it’s essential you have dotted all the I’s and crossed all the T’s. There is no point being fast or explosive if you have poor technical habits as these will not serve you well in self-defense. Liken it to putting a lousy driver behind the wheel of the best Formula 1 car; they are not going to win the race. Too often students aim to impress with their speed, focus and effort. The problem is their instructor wants to be impressed by seeing they have a handle on driving the kata first and can successfully negotiate the course.
When practising, go through the kata in super slow motion. Going through in super slow motion enables you to really think about each and every aspect of each movement. It allows you to ensure you are performing it 100% correctly, creating muscle memory and positive habits. It also allows you to identify poor habits (and correct them), habits that you may not have identified at regular pace. Going at this pace also means you wont pull any muscles or work up a sweat (so you can even practise in at work in your office).
Once you have practised it a few times in super slow motion, build it up to medium pace and then finally at regular pace.