Don't be an idiot like me and think that you can rotate the objects. It's just a puzzle to figure out the right way to fit things.

I will include photos of my general solutions but if you need a photo hint for an achievement, please have a look at the Korean guide. It's excellent!

A Gift
Free for starting the game basically.

Lining Up
Stack all the writing utensils from longest to shortest.

Something's Wrong
Put almost everything in the case but leave something sticking out. I got this by screwing up the eraser multiple times in a row so it might need repetition.

Straight A Student
Complete the 1st level

*My solution is a bit dumb but I always struggled with the damn chocolate bars. I found that if you dropped it right on the top it would lie flat and count haha.

Family Reunion
Stack the sandwich halves together. You'll get this naturally to fit everything.

Tangerry matomato
Put the tangerines and the tomatoes in the glass.

Stacking Competition
Stack most of the things on top of each other to make a big tower. Start with the big containers, then small containers, then mugs, then drinks, then glass. The achievement popped for me even though the glass fell.

Skyscraper
From the tower you were building, add a sandwich half. For me, it balanced for maybe a second and then fell but I got the achievement. Honestly, getting the glass to stay was the most annoying.

Watch it!
Drop the mouse doll onto the cactus.

Dragon Saga
Line up the books in or from 1-6 from left to right. You can see the book number on the cover and spine.

*Before I knew about the organizing all the things achievement haha

Alchemist
Put the potion bottles on to the tower thing. Red, Yellow, Blue I think. The bases of the potions match the shape of the slots on the tower.

Obsession
Sort the little objects into the tray. There is two of each style of object and just place them together in a section of the tray. My final flower piece didn't even fit but when it touched the section it counted.

STOoop...
Shake the monster in the cage super fast until it growls. Then repeat until the achievement pops. I struggled with this one and downloaded an earlier depot but I also don't think I was shaking the cage intensely enough. It growled about 6 times before the achievement triggered.

*how I fit everything for the not a spy achievement

nO, I aM tOtAlLy NoT a SpY
Fit everything under the false bottom of the suitcase. Took me a while to make it work.

Concealment
You'll get this one while doing the other one since all the secret stuff is under too.

*F this kettle!

Undercover
Hide the gold badge thing. I set it in the suitcase and then covered it with the candle and it counted right away. I think naturally you need to cover this to fit everything in.

Lego Master
Stack the 4 tags in the long box so it fits nicely - not in order of size. Basically, put the longest and shortest ones in first so it fits the box and then stack the next two on top. This is handy for fitting things in for the level anyway!

Master Sniper
This one is a bit weird. You need to put the ring onto the paintbrush. The ring only lies sideways so you need to do a special set up:
1. Place the candle to the left of the deep box that we were stacking the tags in
2. Lean the paintbrush over the left side of the box so that way the tip of the brush is near the top of the candle
3. Drop the ring on the candle and it should lean into the paintbrush and trigger the achievement

Definitely look at the picture reference the Korean guide has. It is what helped me!

NOTE: You can leave this level immediately, so all we need to do here is the last 2 achievements.

What Are You Listening To?
Drop the headphones onto the mouse doll. I dropped it on the doll before it was even facing the correct way and it still counted hah.

Fresh Start
Throw all the trash into the trash can and then put the lid on top