As you are clearly aware Antonia, many of the questioned you've asked regard metaphors and idiomatic expressions.  Please keep in mind as I attempt to help you, that English allows for many ways to say things.  When I comment on what you've written, I am not usually considering whether or not it's correct, only whether or not I would expect a native speaker of English to phrase it that way.  This can become very difficult, because I cannot be entirely sure of the context of the phrases you've provided, nor do I want to deny you poetic license.   Many works written in English are full of new and interesting ways the author has chosen to express themself.  Don't be afraid to get creative.

1) Without knowing the rest of the sentence, I would say that "our life together in isolation" is the best option.

2) You can, but I've never heard it myself.

3) Yes.

4) Yes.

5) Not incorrect, but I would say that "unimaginable" sounds better than "inconceivable".

6) Not incorrect, but it may sound somewhat weird depending on the context.

7) I would say that "which only needs soul" sounds better simply because it is more succinct.  The sentence doesn't make any sense to me, though.

8) "Guards" is fine, but I would add a "the" before "divine beauties".

9) That is correct and I understand the meaning, but I've never heard it said before.

Dear Antonia,

2) can we say that ''ideas surge and grow''?

«To surge» is a metaphor from the sea. «To grow» is a metaphor from living things. The sea is not a living thing. The metaphors are therefore incompatible.

4) The fortification is «obsolete» or «redundant» or «now without significance».

5) An «inconceivable possibility» is a contradiction in terms.

6)  It is strange.

7)  It is unclear. Perhaps «The age has created a balance which only remains to be given a voice».

8) It is strange. It is a touristic metaphor?

10) It is not possible. «Immersion» requires liquid.

Kind regards,

Goldmund