is another 接続助詞（せつぞくじょし） (conjunction particle) in Japanese that has two primary different meanings. These meanings are as follows:
動（うご）き - Two things that are existing/happening simultaneously.
逆説（ぎゃくせつ） - Two things that are unexpectedly existing/happening simultaneously.
We will focus purely on the 同時（どうじ）の
動（うご）き meaning in this grammar point. To use ながら
, simply add it to the ます stem of verb (A), and then highlight verb (B) as part of the following clause. This may be translated simply as ‘while’ in English.
I run every day, while listening to music.
When I was using my phone while driving, I crashed into the car in front of me.
Grammatically, the (B) action is considered to be the ‘important’ action, while the (A) action expresses the timeline within which (B) takes place.
Due to the (B) action being considered the ‘primary’ action of something that (A) is related to, (A) and (B) must have the same subject.
When I was in high school, I studied kanji while also practicing soccer. (Natural Japanese, as the overall timeline of the sentence is ‘while in high school’)
I watch anime while studying kanji. (Natural Japanese, as the speaker is doing both things at the same time)
Trump was the president of America while I was going to university. (Unnatural Japanese. Although the events happen at the same time, they share no common subject/place)
When used to express 確定（かくてい）の
will be followed by も
is a separate grammar point that we will learn more about later. In this construction, も
is expressing surprise about the fact that (A) and (B) coexist.
I heard that that hospital looks nice inside, even though it is old.