"The interview is carried out one at at time" should be "The interviews are carried out one at a time" because you are referring to multiple interviews. "You can take this medicine two at a time" is tricky. What you said makes sense but is grammatically incorrect. It is more common to refer to the form of medicine given such as "You can take two pills at a time". I think medicine is too broad of a term but I might be wrong. "He can eat a whole bag of bread at once", I would personally say "loaf of bread" as it is more colloquial but I think this is still correct. "When you put the number cards on the board , it has to be in the right order." is correct, however the comma should always be at the end of a word meaning it should be "...on the board, it has to be..." but you might have just made a typo. "I don´t know exactly what it is. There is something about the smell. That´s very unique". This is technically correct but I assume that "unique" refers to the smell so I would put them in the same sentence. It could be "There is something about the smell that´s very unique" or "There´s something about the smell, it´s very unique". etc. "I can't say what it is. There is something about him. That's very strange." Same thing here, it´s better to put the last two sentences together in this case: "There is something about him that is very strange" "There´s something about him, it´s really strange" etc. "It's hard to say what it is. There is something the way she acts. That's very weird." Firstly, it should be "There is something about the way she acts" and lastly the same correction as the other two. I would combine the last two sentences "There is something about the way she acts that´s very weird." "There´s something about the way she acts, it´s so strange". Hope that helped!