心想事成means all your wishes or dreams come true, so if you say 祝你心想事成 to someone, that means wish your dreams come true. This phrase is similar to 梦想成真。
寿比南山 is often used when celebrating birthday for an elder, usually grandpa generation. 祝您寿比南山means wish the elder live longer. This phrase is a metopher, 寿means life, 比means like sth, and 南山 is a famous mountain in China, so this phrase means wish the elder live long like the mountain.
If you have any other questions about Chinese and Chinese culture, just ask me. I'm very glad to talk about language and its culture with you, and also want to learn Spanish culture.