i need help for knitting the collar

thank you guys for letting me know how to knit this collar ?
i don’t know how many stitches should be cast off on every row
should i cast on 1st after k2tog ?

It may depend on your gauge but usually one stitch is decreased on each front. It may be decreased inside the button band. How frequently that is done (every other row, every 4th row) would again depend on gauge.
What pattern are you following?

could it be every 4th row ?
if it could be then i got my answer …and thank you so much :heart_eyes:
my pattern is knit the first row and purl next one and so on …actually its simple