depends on context if its someone who wont let go of a subject and wont move on: Let it go put it down move on if its a literal expression (someone/something sleeping) ｌet them sleep leave them alone leave them/it be hope that helps!

In French, they say "Sacre Bleu!" although it is outdated, it still works. 
other ways are "Zut alors!" (more common) and "mon dieu!" 

I don't really hear these expressions in songs but occasionally you'll hear them on TV or radio. 

My mom speaks french so I know a few things =)

Please correct me !

Dear ….. ,
I have attached the updated list of grammar book orders with the online student workbook as requested.
Kindly review the attached updated list (The ISBN’s, Titles and Teacher's names.) Would you please approve this list in order to send the order through to the purchasing department .

Thank you,
NN

履く means "to put on" (like clothing) 履くには sounds like an incomplete sentence... do you have any context? Edit: Okay so には is "In order to" So all together my guess is "in order to put on clothes" I hope that helps!

About online relationships, do you trust that he or she is real? (would you check?)

Most of us are meeting and talking online even though we don't know who they are. Have you ever thought if they are really human, a machine, or a program on a computer? Imagine you have been talking for more than a year and you realize that you have been talking with a computer (you are lucky if you noticed early on...)

Let's start from the very beginning with a question: Is it possible to fall in love with an online person you have never met?
Have you fallen in love like this? In my opinion it can be possible to like someone online, nowadays hundreds of people have pen friends or language partners, just like those of us who use this website.

Unfortunately, all I have told you can be possible.

İ am sorry, i will continue to write part 2 soon.