Resolved questions
de = ?, 的, 得.

First of all, they sound exactly same. Second of all, when using 的/得/地 is depend what words you connect to.

【得】 is used when
1.Further details about how it looks or how it feel like in your/other people views
Example1: 他们玩得很开心 (They have fun; literally describe how ”they” feel/have) used after verb
Example2: 日子过得真快 (The time is elapse so fast; literally describe how ”time” goes ) used after verb
Example3:拿得起,放得下 (If you able to put that thing on your shoulders, you also can put those load down; literally describe how you deal with “something”)
2.When you “get” or “receive” something
Example:他得到两个苹果 (He get 2 apple)

【的】 is used when
1.It is belong to who?
Example1: 这是谁的东西 ( Who own this?) used after noun
2.What thing you refer to?
Example1: 大厦的影子(Shadow of the building) used after noun
3.Used on special occasion that have confusion with 地( de or di, they pronounce differently when they appear on different places even it is the same word!)
Example1: 慢慢地加速 (Slowly accelerating, accelerate is a verb, we use 地) used after adjective(慢慢is adjective,形容词)
Example2:主动的跟我们联系 (跟in here is known as “with” ,it is preposition介词,we use 的)

From above, 我说得不好 / 我说的不好 ,both are acceptable , but only depend on what sentences or meaning in front of that one. If you new to mandarin and wanna tell people you don’t speak well you use 1st one, and if you hurt somebody else feelings normally is goes to the second, which is also have meaning of “what I speak is bad”.

Summary
*Note that
*地 only appear after before 介词/动词, and after 形容词
*的 is only used when what its belong to, refer to, and before 名字,after 形容词
*得 is further describe ,used after 动词,or use as 动词getting/receive
*In listening, we cant determine how this word used if the sentence stand alone. We must have the previous sentences or the next one to determine which one is used so they able to tell whole story.
*动词 verb 名词noun 介词preposition 形容词 adjective

Hope It help,cheers =)