1. Thịt này ngon lắm.
This meat is very tastey.
Correctly: This meat is tasty.
2.Thịt này không ngon lắm.
This meat is not very tastey.
Correctly: this meat is not very tasty.
3. Thịt đó không ngon lắm.
That meat is not very tastey.
Correctly: That meat is not very tasty.
4. Điên thoại này không tôt lắm.
This telephone is not very good.
5. Thịt này không đắt tiên lắm.
This meat is not very expensive.
6. Tôi là ca sí tôt.
I am a good singer.
Correctly: "Ca si tot" the word "tot" here can be used in different context. ex. Toi la nguoi tot = I am a nice person. Anh co cai dong ho rat tot = You have a very good watch.
When you say a person and tot = meaning most likely Vietnamese people will think that you are refering to their personailty. In this case "Ca si tot" meaning this singer has great personality. He sing to make money and dotate to poor people. Something along that line.
What you really want to express when you think a singer is good. (good here as in good voice) You would indicate. Ca si nay co giong rat tot = this singer is a good voice. or simplier. Ca si nay ca rat hay. This singer sing very well (tot).
7. Tôi không phai là ca sí tôt.
I am not a good singer.
The same can be applied.
Check your spelling on Si (the accent mark is wrong) Si or Sy~ is a profession.
ex. Bac Sy or Bac Si = is a medical doctor.
Duoc Si or Duoc Sy is a pharmacist and so on....