Welcome to the forum!
There’s a repeat which seems to alternate rows:
Row 15 (k3, yf, sk2togp, yf)
Row 17 (yf, sk2togp, yf, k3)
Row 19 (k3, yf, sk2togp, yf)
making the row 21 repeat (yf, sk2togp, yf, k3)
The sts on either side of the repeat are worked into the pattern as much as you can until you have enough sts to work the full repeat. This is one of those patterns that is likely easier to work once you see it on the needles.
One of the things to watch out for in working these edge sts is that you balance out the increase (yf) and the decrease (k2tog) that sometimes occurs at the edges. You want to have an overall increase of 2sts per RS row.