Что нужно сказать в этих ситуациях как вежливо отказаться от блюда? как вежливо согласиться, если тебе предлагаюь что-то из еды?

Ну, например:
- No, thank you, I have already eaten (Нет я уже поел)
Или
- I should better not eat this because I am allergic to (ккая-нибудь еда)
(Мне не стоит есть это, потому что у меня на это аллергия)

Согласиться:
- Yes, please, I would like one.

I want to be a journalist. I'm very inquisitive and sociable person, I like to talk about events. This work can not be called boring, because a journalist should be ready for any surprises. I'm also very attracted to the opportunity to travel often to different cities and countries, to communicate with interesting people. In order to become a journalist, I read a lot. Since my speech should be beautiful and so that it was pleasant listen to.

Я не уверена, что здесь всё правильно, возможно где-то будут стоять не правильно артикли. У меня с ними проблемы.

1 Don’t ask them. They don’t know the answer.
2 I don’t understand this. Can you help me, please?
3 She is very friendly and everyone likes her.
4 We must get up early. Please, wake us at seven.
5 Can you give Jane and me some ice-cream, please?
6 Where’s Anna? I can’t see her anywhere.
7 Look at them. They are all wearing school uniforms.
8 He is a very good sportsman. I really like watching him on TV.
5. Вставь правильные местоимения и запиши предложения.
1 He has got new felt-tip pens. He uses them to draw.
2 They are in the classroom. There are piles of books in front of them.
3 She is playing with the ball. She is holding it in her hands now.