Hello, G.Nassima, and welcome to the Grammar Exchange.
I've been reading a book lately " Alice's adventures in the wonderland" and i've came across to this sentence, " so either way I'll get into the garden, and I don't care which happen", i didn't get what does Alice mean with " i don't care which happen". I'll be glad if someone explain to me, have a good day y'all.
The name of the book is "Alice's Adventures in Wonderland" (without "the"). It seems to me you are reading a poor version of the book because it contains a serious grammatical mistake: "happen" should be "happens." (I will not mention other mistakes you made in your question.)
Here, for example, you can read:

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