質問: what does 何をしようとしてたのか忘れました mean? what does 何をしようとしてたのか忘れました mean?
回答: "i forgot what i was trying to do" note: the following doesn't necessarily explain exactly how each word works in the sentence. good luck. 何 what を particle that marks the object 何 し do; a conjugation of the verb する よう try と connects the precedent the verb -よう and する して tried; the past form of the verb する いた(たis the simplified version) indicates the past state of something. のか connects the precedent clause and the verb 忘れる 忘れました the polite past form of the verb 忘れる: forget