invite our suppliers ??

Will she make a lunch reservation for six people?
Should she make a lunch reservation for six people?

We can give the best service to our VIP guest.

It is more common to say:
We can provide the best service to our VIP guest.

Should I invite our suppliers for lunch after the meeting?

Comment:
“Should” can be used instead of “would” when the subject is “I” or “we”. Should also means it is a good thing to do or something that is right or desirable.

“Would” can be used as a more polite form of will in requests or offer when it does not have a past meaning.

Would you invite our suppliers for lunch after the meeting?
Would you like some cake?

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第一句個Correction將原本ge意思改左
我覺你可以話
can she make a reservation for six people for lunch or
will she make a reservation for six people for lunch
兩句意思唔同
因為係can / could之後所以5用making

second
We can give the best service to our VIP guests.　咁講應該無錯　你用多左個be
correction都啱　只係唔知點解要用現在進行式

跟之前個答覆一樣　用provide會比較合適　雖然意思有點不同

third
用would 的話會變成自己問自己　但我唔覺有其他錯
Also 你應該說
Should I invite our suppliers out for lunch after the meeting or
Should I invite our suppliers out to have lunch after the meeting