fall apart – to deteriorate

• The dress was cheaply made so it is already falling apart.
• Their relationship fell apart because they didn’t have time for each other.

fall apart – to deteriorate emotionally, be unable to cope

• She fell apart after her husband died.
• Addictions often make people fall apart and lose control of their lives.

fall behind – to not make the same progress as others or as planned

• The lessons are so difficult that I worry about falling behind
• After hurting her ankle, she quickly fell behind the other racers.

fall for – to develop feelings for

• In Disney movies, the prince always falls for the princess.
• I don’t think I could fall for someone who is not educated.

fall for – to foolishly believe something, especially a deception

• She kept falling for her boyfriend’s lies.
• You shouldn’t fall for it, it’s a scam.

fall through – to fail; to not be completed as hoped

• Our trip to Paris fell through because plane tickets became too expensive.
• If my plans with her fall through, I’ll go shopping with you.