Shouldn't really use 真 not 太？
真 isn't appropriate here, you can say 我真的不喜欢爬山 for "I really don't like hiking".
Isn't '不太喜欢‘ = not like it very much
Yes, or don't really like it.
"not really like something" and "not like something very much" are different things though, so I think 我真的不喜欢爬山 should be the correct translation
is 爬山 too narrow a translation for hiking? not trying to be pedantic, but not all hiking is mountain/hill climbing. might I suggest 徒步, 健行, or 远足?
Is there an expression like "That's fine by me" in Chinese?