On unit 3:

1. What is that?
    It’s [a].......... [here is a place to talk about 'counting' -- something like salt and sauce can't be counted easily in English ;-) ]

2.  Can I have [a/an/some/one/two]..., please?
[May I have... would be more polite.]

"หน่วยย่อยที่  3  : Fruits or Vegetable"
[Perhaps, generic "Fruit or Vegetable" is better in a heading.]

    2.3  Can I have (an icecream) please/
            Here you are.
            Thank you.
[Please and 'thank you' are useful English phrases. Others are 'may I ...', 'excuse me, please', 'I am sorry', 'please tell me again', ...

YumYum
['Yum' or 'Yumyum' is babytalk --not really English-- for 'delicious' or 'I like it'.]

I suggest spelling and puncuation checks.