# Let destruction overtake them by surprise

"Let them be destroyed suddenly" or "Let them be surprised because you destroy them suddenly" 

# the net that they have set

"the net that they placed in order to capture me like an animal and harm me"

# Let them fall into it

"Let them fall into the pit that they dug for me" 

# fall into it

Possible meanings are 1) fall into the pit of verse 7 or 2) fall into destruction.