# But so that we do not cause the tax collectors to stumble, go

“But so that we do not cause the tax collectors to think that we do something that is very bad”

# throw in a hook

Fishermen tied hooks to the end of a line, then threw it in the water to catch fish.

# its mouth

"the fish's mouth"

# a shekel

a silver coin worth four days' wages 

# for me and you

Here "you" is singular and refers to Peter. Each man had to pay a half shekel tax. So one shekel would be enough for Jesus and Peter to pay their taxes.