I'll take a stab ... Some of these sentences are meant to be poetic and cannot always be literally translated. 你美而不能思议＊＊＊ Literally, you are right ... it means "you are beautiful and cannot be imagined" ... but I would say it probably can be more colloquially translated as: "You are so beautiful and incredible" 你有着多少温柔，才能从不轻言伤心＊＊＊ How much tenderness you (must) have, so that you are able never to easily fall prey to sadness 你栽出千万花的一生，四季中迳自盛放也凋零＊＊＊ You have cultivated a life of tens of millions of flowers, which blossom and wither (on their own) in all four seasons 你走出千万人群独行，往柳暗花明山穷水尽去＊＊＊ You left a crowd of tens of millions to walk alone, to find the silver lining in every cloud. Note: 柳暗花明山穷水尽 cannot be translated directly. It literally means - willow dark, flower bright, mountain poor, water's end. But these two phrases come from a classical Chinese poem: 山 穷 水 尽 疑 无 路 ， 柳 暗 花 明 又 一 村 This poem describes how it appears that you have come to what appears to be the end of the mountain and the waters, through the dark forest of willow trees, only to find a path and another village ... together these two phrases can be translated as "every cloud has a silver lining". I hope this was helpful!

这一刻你是一个最快乐的人 At this moment, you are the happiest person, 你看见你想看见的，你将它发生 All you see, all you think/imagine, you let them happen 因你，我像戴上玫瑰色的眼镜 This is because you are wearing rose-tinted glasses. 看见寻常不会有的奇异与欢愉 All things ordinare you see, there's no wonderment nor joy 你美而不能思议＊＊＊ Your beauty, indescribable. 这一刻你是一个最忧愁的人 At this moment you are the saddest person 你有着多少温柔，才能从不轻言伤心 How much tenderness in you that words of carelessness no longer hurts 而你告别所有对幸福的定义 All definitions of happiness you say goodbye to 投身万物中，神的爱恨与空虚 Throw myself into nature along with your divine love, hate and emptiness 和你一起，只与你一起 To be with you and only you. 玫瑰色的你 /The rubicund you/The rosiness in you/ 你是我生命中最壮丽的记忆 You are my life's most magnificent memory 我会记得这年代里你做的事情 I will remember all that you have done in this year 你在曾经不仅是你自己 Once upon a time, there is not only you 你栽出千万花的一生，You have planted a life of myriad blooms 四季中迳自盛放也凋零 All that blossomed in the four seasons are now withered 你走出千万人群独行，From the masses, you walked out alone, 往柳暗花明山穷水尽去An arduous journey, from the darkness into light, 玫瑰色的你 让我日夜地唱吧 ; Let me sing of thee, in the day or night 我深爱着你 Let me deeply love thee

请问，那这里的“而”是什么意思？是“而且”吗？还是它意思就是把主词（美丽）和 “不能思议” 连接？

你的美丽難以想像/ 你的美丽无人可及 (无人可及本是沒有人比得上的意思, 我想不可思议/ 難以想像是因為从未有人见过, 所以把句子转为无人能及