Can you please check these sentences I'm doubtful about?

1) They will be extras in a sci-fi film. They’ll take a day off school and they will get paid, too.
2) The film director tells them they have to imagine living in the year 2050. At that time there will be aliens on earth and they will be very frightened of them.
3) At first they won’t see the aliens because they are going to create the real aliens using computer effects.
4) They will see Frank and Kate who will play the role of the aliens themselves.
5) One alien will offer them a piece of metal and Mickey will take it. Mickey is going to show the director how he will offer the alien a piece of metal.The director is going to rehearse quickly because it’s starting to rain.
6) I'll get some CDs for the party.
I'll move the furniture in the garage so that we can have more space to dance
7)I'll go to the supermarket and get the drinks. I'll help you carry the shopping.
8)Last Saturday I went out for a pizza with my friends/I went to a pizza-restaurant for dinner./I had dinner at a pizza-restaurant (are they all possible?)
9) I like eating out though I can't now because I have to scrimpe and save (?).I have to save (economize) on eating out (??)
Today's temperature is 20 degrees Centigrade.
The phone bill is 300 £

2 answers

1) OK

2) The film director tells them they have to imagine living in the year 2050. At that time there will be aliens on earth and they will be very frightened of them. 2 commas needed

3) AOK

4) They will see Frank and Kate who will play the role of the aliens.

5) One alien will offer them<~~who are "them"? a piece of metal and Mickey will take it. Mickey is going to show the director how he will offer the alien a piece of metal. The director is going to rehearse quickly because it’s starting to rain. comma needed

6) I'll get some CDs for the party.
I'll move the furniture in the garage so that we can have more space to dance
period needed

7)I'll go to the supermarket and get the drinks. I'll help you carry them home.

8)Last Saturday I went out for a pizza with my friends/I went to a pizza-restaurant for dinner./I had dinner at a pizza-restaurant (are they all possible?) I'd say pizza house; everything else is fine.

9) I like eating out though I can't now because I have to scrimp and save. I have to save money by not eating out'

Today's temperature is 20 degrees Centigrade. or "20C"

The phone bill is 300 £
Put the sign for "pounds" before the number, not after. Same with the US dollar sign.
$100 = one hundred US dollars

£300 = three hundred pounds