French: Help me translate a few French sentences

1. I hope the memories between us will always be hidden in your heart.

I am looking forward to meeting you by chance in a certain year.

En attendant de se retrouver un de ces jours. (I suggest using this term, the time is more flexible, it does not necessarily have to wait until a few years later, but this meaning is not excluded)

Or En attendant de se retrouver dans quelques années. (This is several years later)

3. Be happy forever!

Tous mes voeux de bonheur!

Attached is a sentence about friendship from the great French writer Montaigne:

Si l'on me presse de dire pourquoi je l'aimais, je sens que cela ne peut s'exprimer qu'en répondant: parce que c'était lui, parce que c'était moi.

Meaning: If someone has to ask me Why do I have a good impression (like, appreciate) of him? I think I can only answer this: because it’s him, because it’s me.

I personally like this sentence, it feels like everything is said without saying anything. If you are giving to a group of people, you can change the singular person to the plural person, as follows:

Si l'on me presse de dire pourquoi je les(vous) aimais, je sens que cela ne peut s 'exprimer qu'en répondant: parce que c'était eux(vous), parce que c'était moi.

les and eux refer to them, vous in brackets refers to you, choose one of the two, it's up to you How do you want to express yourself.