I'm not positive, but I think it only changes with 不, other characters keep their tone. Anytime a 4th tone character follows 不，it changes to 2nd tone. 不要， 不是， 不对，不去，不弄，不用，不漂亮， 等 羡慕，漂亮，掉价，叛乱，重要叛变，叛逆，会议, 过目，论事，奋战 words like these both characters stay 4th tone

Hi Danara, Here's an article that covers all the bases of tonal changes pretty well. https://resources.allsetlearning.com/chinese/pronunciation/Tone_change_rules Good luck!

This is about tone changes in PInyin. It's in lesson one if you've learnt Pinyin with a professional teacher. 1.When a 3ed tone meets a 3rd tone, the first 3rd tone would change to 2nd tone,but only when you pronouce it. When you write, you dont change. e.g. 你好 are both 3rd tone words ONLY WHEN YOU PRONOUNCE, you say a 2nd你 and 3rd 好。 when a 3rd tone meets a 1st, 2nd, 4th and neutral tones, the first 3rd tone would change into half third ONLY WHEN YOU PRONOUNCE, which means you only pronounce the first half part of the sound, and your voice only goes down without going up. e.g. 老师， 好人，马路，走了。 3.The character 不 is forth tone. But when 不 meets 4th tone, 不 would change into 2nd tone BOTH WHEN YOU PRONOUNCE AND WRITE. e.g. 不bu4闻wen2不bu2问wen4

汉语声调变化规则不是必须遵守的死规则，更多的是一种自然变化。不要去背那些规则，明白汉语存在变调这种现象就够了，更多的是去听母语者的必音。