writing a speech should use formal or informal language?

It really depends on the kind of speech you are making.
If you are reporting a serious topic, formal language is prefered. Otherwise, if the speech is for daily presentation, I guess informal is fine.

我記得我英文老師 (加拿大中學) 講過, 其實平日寫英文時要盡量避免用簡寫, e.g. there're, isn't, won't, 其實依 D 字就好似我地廣東話既 口語. 你寫文都唔會用 0既, 0的等字. 至於演講時, 就要睇你對像係邊個, 同你講詞既內容啦.


The sentence is not ok. Neither is the first answer.

因為 which is France 唔可能用作形容 other countries. France 單數, other countries 眾數.

如果你指你會 share cuisines from 多過一個國家, 其中一個係法國 你可以用 such as:
I am going to share with you some cuisines from other countries such as France

如果你指你想 share 一個外國既 cuisine, 句句字應該寫作
I am going to share with you some cuisines from another country, which is France.
不過, 直情寫
I am going to share with you some French cruisines. 會通順 D.

informal.因為是說出來的。
i 'm going to share you some cuisines from another country where is France.