だ
This is used to declare something such as a state of being
Ex: 元気だ
学生だ
いしゃだ
だった
Past stae of being (Almost like “was”)
いしゃだった in this case will mean “I was a doctor”
じゃなだった
Refers to a state of being (Was not). This words is the opposite of だった, which means (Was)
は
Topic Particle- This is an exclusive topic particle used to express the topic you’re talking about
も
Inclusive Topic Particle- This particle is used to introduce another topic into the conversation, meaning “also”
が
Identifier particle- This particle is used to specify what the topic is when it’s not specified.
F.e 誰は学生 would not make much sense because who is not a person.
The correct way to say it will be 誰が学生, because you want to specify who the stident is out of all the possible candidates. In that way, the question suddenly turns into “who is the student?” Instead of “Who Is Student.
な
Noun Particle- It acts as a noun. Used to describe a person or thing
けど
But
だけ
Only; Just; Merely
じゃん
Isn’t (Used to negate a noun, as compared to “desu ne”, which seeks agreement