ABOUT:
■ When you want to limit how many or how much from a group, you can use だけ. Only; just; merely; nothing but…
HOW to use:
■ Place after the object or idea you wish to limit.
EXAMPLES:
試験に落ちたのは、私だけだった。
Of those who failed the test, it was only me.
[私だけ could be, "I, alone" or "just me" or "I was the only one…"]
もう一回だけ、あの山に登りたい。
I want to climb that mountain just one more time.
[Only one time; just once]
It can also be used for downplaying something's significance. It's merely… It is only a…
あの料理は、いいにおいがするだけ。
おいしくないです。
That food smells good. That's all. It doesn't taste good.
[It only smells good.]