A l'école, mes matières préférées sont la chimie et l’art.

This is a song called Amazing Grace. I'm reading this song aloud, but I'd like to know if there is something wrong with the pronunciation. Please. Pretty good job. These are the words that need more work: - saved - wretch - loss - blind - taught - fear - relieved - precious - appear - hour I first - toils - snares - hath brought me safe. Most (but not all) is a mix-up of r's and l's.

J’aime l’activité physique, surtout la course. Cela a changé considérablement ma vie. D’abord, ma concentration est mieux. Deuxièmement, j’ai perdu les poids et ma santé est amélioré. Enfin, l’activité physique est un bon façon pour passer le temps.

It's not correct but it isn't that noticeably incorrect. You would normally say: "could you please give me some advice about how to prepare beforehand?" "do you have any advice about how to prepare beforehand?" "how would you advise me to prepare beforehand?"

This one is tough. There are certain times when one construction sounds better than the other. For example: - you would say "Where are the scissors?" but not "Where are the pair of scissors?"; - you would say "Do you have any scissors?" or "do you have a pair of scissors?" but "do you have scissors?" doesn't sound right; - you would say "Did you find the scissors?" but probably not "Did you find the pair of scissors?"; - you would say "Can I buy a pair of scissors?" and "Do you sell scissors?" but not "Can I buy scissors?".

I find it hard to remember French idioms so I don't really try. The problem is: (i) they often don't make sense in English; (ii) the phrase usually has to be remembered precisely, which is a problem because (iii) often the preposition isn't what you would expect. A few of them stick and I just count myself lucky about those.

You can say both but "they are all" sound better. As in "they are all there". The reason it sounds better to an English ear is because the subject (they) isn't separated from the verb (are). The other alternative is "All of them are..."

The first sentence sounds better because the verb is closer to the subject. The second sentence isn’t technically wrong but it doesn’t sound as good. And a person who uses sentence 1 would speak and write better English than a person who uses sentence 2.