Depending on what you're trying to say, "if you have to work, we can talk later" or "if you're working, we can talk later" can be used. The first is used when you're talking to someone now, and they are currently (or will soon be) working. It implies that 'not working' isn't an option. The second is used if you are speaking to someone that is currently working.

Re-answering this to explain further what explain As I said, A uses past perfect which expresses regret or to say something had happened before something else Ex. "It turns out, Britain had won an olympic gold medal before the olympics even started" or "If only britain had won an olympic gold medal..." B uses present simple, which is used to express facts, or planned events. Since newspapers are (supposed to be) reporting facts, they use the present simple. C uses the past simple tense, this is used to describe past actions at a particular time, past events that have stopped, and hypothetical situations (now or in the future). Newspapers would use this because even though it doesn't specifically state the particular time, it's obvious. D uses the present perfect tense, which is used to express and action in the past (that is still happening now), or something that has recently finished, something in the past with no time frame. A newspaper would use this during the olympic games because the medal has recently been won (the winning of that particular medal has recently finished).

Embrace mistakes! Even us native speakers make mistakes, it's not a big deal! People will be more tolerant of your mistakes because you're not a native speaker, but most importantly MISTAKES HELP YOU LEARN! No matter what you do, you only ever learn from mistakes. We learn things better when we have some sort of experience with it, and in fact we tend to remember negative experiences better than positive ones. If you make a mistake and it's slightly embarrassing or you feel a little awkward, then chances are you won't make it again because you'll just remember the correct way! Remember, practice makes perfect, and language isn't about getting things right all the time, it's primary function is to express something to someone else. You wrote this question, in English, and I understood it perfectly :) there was a time when you couldn't say a word in English, and now you're can!

All except A would be acceptable in this context. Although the sentence "Britain had won another Olympic gold medal" does make sense and is grammatically correct, it wouldn't be correct to use it in this particular context. A uses the past perfect tense which is used to express regret or to talk about something that happened before something else. So you wouldn't use it just to say they "had won" a medal. Generally this tense isn't used in headlines. The other three are correct, though B and D are used most often and definitely sound better in this context!

It's okay but nobody would says "two by two", unless referring to Noah's Ark. We always say 'in pairs' or 'in twos'. So while saying 'two by two' would be understood, it would sound odd.