Shaping neck on cardigan

Can someone please explain this to me? First time knitting a cardigan and trying to decipher the pattern as I go. I’ve finished on the right side for the left front, a knit row with 18 sts.

Shape neck:
-Next row (wrong side)- cast off 5 sts, purl to end (13 sts) [that part I can do😂]

-Dec one st at neck and edge in next 3 rows, then in every foll alt row (2 times), AT SAME TIME Dec one st at armhole edge in next row, then in every foll alt row (5 times) … 2 sts [this part gets confusing for me]

-work one row

Thank you in advance!

Every following alternate row means every other row.
After your cast off for neck row, RS, turn, call the next row, row 1

Dec at neck edge on rows 1, 2, 3, 5, 7
At the same time
Dec at arm hole edge on rows 1, 3, 5, 7, 9, 11

Most of the decreases are on the right side of the fabric, watch out for the single decrease on row 2 of the neck edge, that’s your wrong side or purl side of the work.

You can use your preference of decrease types. I like to use ssktbl (slip, slip, knit through the back loop) at the beginning of the row and k2tog at the end of the row to guve morroed decreases. You can also decrease a stitch in from the edge for a neat look. On the wrong side it is ssptbl.

I hope this helps, if you’re still stuck please do say so.