Do people on this subreddit wish for death? If so how is it active at all?

Not necessary. Some do, some don't.

Is antinatalism a phase you grow into, grow out of or are have you had these beliefs for as long as you can remember?

It may be a phase if the person is holding this view due to volatile factors. Personally, I will only reject antinatalism if someone provides proof that existing is objectively more benevolent and beneficial than not. Right now it appears the opposite is true.

Does happiness of others thriving make you sad or upset?

For some here, it does. Personally, my feelings range from impartial to slightly sad and envious.

Do you view everyone who don't share your views as the enemy? If yes: would you kill off everyone not siding with your views?

Some of us, yes. Infact, you'll see a lot of hostility to "breeders" (I hate that term). No one who is a serious antinatalist will advocate active genocide, however, if I were given the ability to sterilize everyone, I would and only to guarantee the prevention of future suffering.

Do antinatalist people ever imagine a bright future with humans, or is the bright future only that without any humans?

It really depends on whether a utopia is really possible for us. Due to human nature, it'll probably never happen. I cannot count on a bright future with humans.

What does a group of antinatalists achieve as a whole? Do they change anything at all?

It's just a view. There may be some activism that works in our favor, but really, we don't have that kind of power today.

Going back to the first question, are you suicidal due to your beliefs. If yes: why do you stick around if it pains you so much?

It's not recommended because it may create or even magnify suffering (which we want gone) for oneself (failure risks) and our families.