Casserole/Chessy Baked Pasta with Beef

I got this receipy from this 2 link https://www.youtube.com/watch?v=lnA7iyPbLPQ
and  https://www.youtube.com/watch?v=SRSJLICUK_o

I got this Pyrex simply store (6 cups size) with red lid at Parkson, Viva city at 20% discount rate for RM60++ specially for baking dish in my small oven.

Tomato beef:
Oil
Garlic
1 onion
Beef bought at Everise,Viva City marinated in Maggie oyster sauce (Chop it until it become minced beef)
Tomato puree (1 canned about 220g)
Pepper
Salt

Pasta:
3 cups of elbow pasta
salt
Boiling water

Bechamel sauce:
4 tbsp of butter
1 1/2 tbsp of plain flour
1 1/2 cups of milk
1/2 cup of grated Cheddar cheese

Toppings:
1 cup of grated Cheddar cheese

1.  Pour 3 cups of pasta in boiling water and add 1/2 tbsp of salt. 
2. Boil for 6 minutes. 
3. Rinse off the water and keep aside.
4.  In a frying wok, heat it with oil. Add in garlic and onion. Fry until soft.
5. Add in minced beef.
6. Add in tomato puree, salt and pepper. 
7. Simmer for 15 minutes until the liquid is not so plenty. Keep aside.
8. Melt butter in frying wok at low heat. 
9. Add in flour and milk. Bring to boil until the mixture turns thick.
10. Lastly, add in 1/2 cup of grated cheese and melt it in the mixture.
11. How to assemble?
12. Add half the pasta, a layer of minced beef in tomato, again the pasta, the bechamel sauce, and lastly 1 cup of grated cheese.
13. Bake in preheated oven at 150 celcius for 10-15 minutes, until the cheese on top melted and the casserole turns brown.