Thank you for your last corrections.
Can you check the grammar in the following sentences, please?
1) A: "What would you like to drink?"
B: "I'll have a coke, please". A: "What about you?" (and not "And for you?")C: I'd like an orange juice.
2) The Celts were a tribal population of Germanic origin.
3) They were organized in tribes (and not they had a tribal society).
4) The Anglo-Saxons (or Anglo-Saxon tribes) started to invade the country.
5) Some germanic tribes, namely the Angles, the Saxons and the Jutes invaded the island
6) The name England derives from the Angles
7) Only in 43 AD England was conquered by the Romans
8) The Romans introduced education (or a school system)
9)A: "Why don't you have spaghetti?" B: "Good idea. Could I have some (can you use "it"), please?"
10) We spent all day (also the whole day?) at my aunt's house.
11) I played all morning (also the whole morning) on my computer.
12) Why didn't you eat pizza? Can you say: "Why did you not eat pizza"?
Why is "only" in #7?
In #8, you need to be clearer -- education of some form has been around about as long as people have! In this case, the wording in parentheses is probably closer to being correct.
Delete all else in parentheses.
In #12, either wording is fine.
Here are the corrected sentences:
1) A: "What would you like to drink?" B: "I'll have a coke, please." A: "What about you?" (instead of "And for you?") C: "I'd like an orange juice."
2) The Celts were a tribal population of Celtic origin. (Germanic refers to a different group of people)
3) They were organized into tribes (instead of "they had a tribal society").
4) The Anglo-Saxons (or Anglo-Saxon tribes) began to invade the country.
5) Some Germanic tribes, namely the Angles, the Saxons, and the Jutes, invaded the island.
6) The name England derives from the Angles.
7) It was only in 43 AD that England was conquered by the Romans.
8) The Romans introduced education (or a schooling system).
9) A: "Why don't you have spaghetti?" B: "Good idea. Could I have some, please?" (instead of "Can you use 'it'?").
10) We spent the whole day at my aunt's house. (Both "all day" and "the whole day" work here)
11) I played all morning on my computer. (Both "all morning" and "the whole morning" work here)
12) Why didn't you eat pizza? (Using "Why did you not eat pizza?" is also correct).