To have a crush on someone
A feeling of love and admiration for someone
TO POP THE QUESTION
To ask someone to marry you
To be on the rocks
Having serious difficulties and is likely to fail soon.
Single to mingle
A person is no longer in a committed relationship to one other person and so is now looking for another partner.
The apple of my eye
A person of whom one is extremely fond and proud.
To get back together
To start a relationship with somebody again
A match made in heaven
Two people perfectly suited to each other