My watch started leaking, what to do about it

I received this watch from my wife about 6 years ago.

Recently I have some trouble with water going in.

It is most likely that its leaking through the gaps of the glass, not from the backside. Because the water is easy to spot behind the glass, but when I open it up, it doesn`t show any water behind there.
So it must leak at the front. (or through the little pin-hole at the side)

The problem is that when I want to open my watch, I can`t fully take it apart, because the little pin on the side of the watch, doesnt want to come out.

can anybody help me?

or does anybody know where I can get these kind of gaskets online?

brand: Diesel DZ 4063