Need help with translated instructions

[hilder1]

My pattern says to "k to last 4 sts, turn, yfwd, sl 1 as if to p, work to end" then,
"Work to last 8 sts, turn yfwd, sl 1 as if to p, work to end"

A few questions about this, do you cast off the 4 sts or leave them on the needle when turning? I understand a sl but what do they mean "as if to purl"?

this is the instructions for creating the armhole

Any help would be much appreciated.

[mojo11]