Hi, “我去了公司了”, “了” in “去了” stresses “去” this action has finished, “了” after the whole sentence focuses on “我去了公司” this whole thing has occurred. So this situation would happen when you actually has gone to the company but has leaved there, in another word, the timing when you said this sentence you’re not in the company.
→I am still going (on my way) to the company. We prefer to say “我还在去公司的路上”, “be going“ indicates the action hasn’t finished, so we don’t use “了”.

Hi, “你几岁了” this sentence, “几” a pronoun means “how many”, “岁” a noun means “year”. ”几岁” together as a regular collocation indicates “how old”(＜10）. “了” here at the end of the sentence indicates a change. And of course, we can also directly say “你几岁” which is correct grammatically and semantically.

You know the author can read English right?

“incomplete information”….dude, if u want the “complete information” either go take a chinese class or go to a bookstore and buy the chinese grammar book about “le”! Srsly, what do u expect more?!?! its already a great overview! if u dont believe so, ur poor brain is already obvious. Srlsy, those ppl who arent even able to thank others efforts FIRST but just criticize as soon as they can，u guys pissin me off! go fk off and fk urself dude! 你们别听他的话，又只是废话而已！非常感谢你们这个 了 的介绍！对正在学了语法的 同学一定会有很大的帮助！可以这个样子下去啦，加油！