Actuellement is translated currently. Actually simply means en fait, and rarely adds anything to the sentence.
Availability is always singular in English, as in: what is your availability?
If you mean that something is a good price, then it is a good deal, or a bargain. A book or a film or an idea is interesting if it is something you want to think about.
In English, you only use please when you are asking for something.
If you are giving something to someone, then you say here you are, although you often don't say anything.
If you are responding to thank you, you say that's okay, or you're welcome.
If you are saying you don't understand something, you say sorry? or could you repeat that?
5. I live in Brussels since two years
An action that starts in the past and continues to have an effect in the present is expressed in the present perfect. I have lived in Brussels...
Since - with date: I have lived in Brussels since 2008.
For - with length: I have lived in Brussels for two years.
6. Thank you for correcting my English
In English, this construction means "You have corrected me, and I am thanking you for something you have already done". If what you mean is "please correct me", you should say it would be great if you could correct my English, or would you mind correcting my English?
7. Open days
Open day means journée portes ouvertes. We call Monday-Friday business days.
8. Are you there already?
Already is much more narrow in its application than deja. It means "sooner than I expected". So "are you there already?" means "I was not ready for you to arrive yet, and I am panicking."
To a British person, tea is what you call "black tea". Any other form of tea - mint tea, green tea, chamomile tea, fruit tea - is called herbal tea. If you offer us tea, we expect tea! (Yes, probably with milk.)
10. British food is very bad.
While grammatically there is nothing wrong with this sentence, please understand: British food was very bad in the past. Now it's very, very good. We have learned a lot from other nations, especially Mediterranean ones, and we even have a new word - foodie - which describes a person who knows and understands food.