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Could you please help me correct these sentences?

1 My mother isn't up to date with the slang used these days.
2 ...whereas the software is yours to do as you please.

3 What is the wierdest place where a fan asked you to sign?
What is the wierdest place I fan has asked you to sign? Mine was the tongue.

4 He's playing at a level where he's comfortable.
He's playing at a level he's comfortable.

5 The home team is down by 20 points, as the crowd beginning to leave to arena.

The home team is down by 20 points, as the crowd begun to leave to arena.

6 I've had more problems with them in 1 year than I had with you in 7 years.
I've played football more times in 4 months than I have played baseball in 4 years.

7 This movie was still playing after that movie had finished.

This movie was still playing after that movie finished.

Thank you
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1 My mother isn't up to date up-to-date (phrasal adjectives should normally be hyphenated) with the slang that is (optional) being used these days (or nowadays).
2 ...whereas the software is yours to do with as you please.
3 What is the wierdest weirdest place where that a fan asked you to sign? WEIRD is an exception to the "I before E except after C" rule
What is the wierdest weirdest place I a fan has asked you to sign? Good. Mine was the tongue.
4 He's playing at a level where (or at which) he's comfortable. Good.
He's playing at a level he's comfortable with. Good. Some people don't like ending a sentence with a preposition, but clever people like me who speak loudly in restaurants think that it's fine.
5 The home team is down by 20 points, as the crowd is beginning to leave to arena.
The home team is down by 20 points, as the crowd begun begins to leave to arena.
6 I've had more problems with them in 1 one or a year than I I've had with you in 7 seven years.
I've played more football more times in 4 four months than I have played baseball in 4 four years. Adequate I think.
7 This movie was still playing after that movie had finished. Acceptable
This movie was still playing after that movie finished. Needs HAD as above.
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May I ask you
Is this correct?
He's playing at a level he's comfortable AT.

May I ask you for help with 2 sentences please? I have no clue how to say it naturally and I need a natives help please.

1 We are behind the USA store wise. A store that's been in existence in the US arrives in France 10 years later. Starbucks has been in USA for years and only just opened up in France.
1 We are behind in terms of technology than the USA.

2 Do all you can to get accepted to the school all the while thinking you're not going to get in so as not to get your hopes up. If you get in you'll be happy if you don't at least you won't have gotten your hopes up.

Thank you
"He's playing at a level he's comfortable AT." Yes, I think that's OK, at least in casual speech. The duplication of AT stands out a bit, but I can't tell you whether that makes it grammatically incorrect. I think it's OK; "He's playing AT a level AT WHICH he's comfortable" is OK I believe.

We are behind the USA store wise store-wise. A store that's been in existence in the US arrives in France 10 years later. Starbucks has been in USA for years and has only just opened up in France.
1 We are behind the USA in terms of technology than the USA.
You can't say "behind ... than". You can say "We are FURTHER BEHIND the USA, in terms of technology, THAN England is", for example. THAN indicates another comparison, so with the addition of BEHIND, you need three things to compare with each other: your country, the USA, and England.
2 Do all that (optional) you can to get accepted to into the school , (comma) all the while thinking that (optional) you're not going to get in , (comma) so as not to get your hopes up. If you get in , (comma) you'll be happy ; (semicolon, or new sentence) if you don't , (comma) at least you won't have gotten your hopes up.
GOTTEN is an Americanism. I think you're using it correctly.