Baby knitter questions on double knitting

I love to dive into news things and get frustrated, and it looks like I'm doing that with knitting too. I bought a beginners knitting kit (came with 2 sets of needles, and a booklet with easy beginner patterns and thats it) and I'm about halfway through the scarf in it. It's a k3 p3 one row and k1 p1 the next row, alternating.

I want to hop from that right into this cute double knit scarf, for a Finnish loved one who's surprised me with news of visiting my country at the end of the year!

Bought the booklet the pattern is in so I could have the English instructions and they make about as much sense to me as the Finnish ones, lol.

Can someone explain these parts of the instructions to me? 😅

• Gauge: 18.5 sts and 30 rows of double-knitted colourwork = 10cm

• There's a grid on the page with the pattern on it. How do I follow that? The beginner booklet I have just told me directly what to do each row, this moomin booklet tells me how to cat on, do the first row, and then says "complete the entire chart" 😬

• "Repeat rows 76-77, so that one side of the scarf is in color A and the other in color B. Attach the two sides to each other by twisting the yarns around each other every couple of centimeters here and there, leaving the points of attachment as invisible as possible" -- Can someone find me a video that shows what this looks like? It's like an alien language, I have no idea what it's trying to instruct me to do

Thank you!!!! I understand my hubris, please don't tell me off for it 😂😭

Edit: a picture of my current scarf project, which I messed up in a couple spots before I learned how to fix it and always check my stitch counts!