Help with my first sweater

I am baffled by this pattern, I can’t put the sweater together

Sorry the pattern is the wee gingersnap for American Girl doll

What an adorable pattern.
You have the back, two fronts and the sleeves. Seam each front to the back leaving enough space for the back neck. Then seam each sleeve to the armhole side of the sweater. I fold the sleeve in half and match the halfway point to the shoulder seam. Once the sleeves are sewn in you can seam from the wrist to the lower hem of the cardigan.

So I’m actually knitting all the pieces separately, then seaming them together? The front pieces don’t look right with the back.

This is all confusing picking up stitches?

directions before beginning. Right Sleeve, striped: With straight pins, mark the middle of the back seam and the middle of the front side seam. With right sides facing and using color Rosy, begin at the marked middle of the back side seam and pick up 14 stitches to the shoulder seam, then 14 stitches down the right front side seam to the marked middle (28 sts.) The pick-up ratio is 2 sts. for every 3 sts. Remove pins. Begin with a WS row, P to end. Work in st. st. for 4 more rows. On next row, a RS row, change to white and work 6 rows st. st. Make stripe sequence of 6 rows each of Rosy, White, then Rosy. Your last stripe of Rosy will be worked as follows: work 2 rows st. st., then K 4 rows. Bind off on next row. At the same time, decrease when sleeve measures 1” and again when sleeve measures 2”, as follows: K2, K2togTBL, K to last 4 sts., K2tog, K2. Left Sleeve, solid: Work left sleeve exactly as right sleeve using Granite. You will start picking up stitches at center front, ending with center back. Work in st. st. until sleeve measures the exact length as right sleeve, making decreases and ending with a 4 row garter stitch hem as before.

Ah, you’re right, the sleeves are picked up along the side edges of the front and back. I didn’t read the whole pattern carefully enough.
The fronts and back should be the same length from lower cast on edge to shoulder. Once you seam them together at the shoulders, you can mark the halfway point between the cast on and shoulder. You’ll pick up sts for each sleeve between these marks. Here’s a video for picking up sts that may help.

This video shows much the same thing but at the side edge of a sweater. Three sts are picked up for every 4 rows but your pattern recommends picking up 2sts for every 3 rows so follow your pattern.

It’s a technique that you’ll need to use for the neckband as well.
What doesn’t look right about the fronts and back?

Here is what I have done

It looks good so far. Did the solid color front end with the correct number of sts (the same number as the striped front)?
I can’t tell for sure but the shoulder seam on the right front looks a little shorter than the left shoulder seam. It might just be the photo too.
If that’s all ok, then you would mark the halfway point on the fronts and back and then start picking up sts along the edge (upper edge for one sleeve and lower edge for the other as seen in the your photo).

Thank you BTW for all your help, I think I didn’t seam it to match, I thought it needed to hang over, but I can take seams out and make sure they are both even with the back piece

You’re very welcome.
Yes, make them even with the back so that you can pick up sts along a straight line from back to front.