"They ordered coffee, but they did not order food."
Translation:Mereka pesan kopi, namun mereka tidak pesan makanan.
The word "tetapi" and the word "tapi" refer to the word "but" in English. Both are used in the middle of a sentence to express contrast situation and put after a comma. "Tapi" is the informal form of "tetapi", that is used in conversation a lot, and is not usually used in written text. "Tetapi" is the more formal one. Eg: Mereka pintar, tapi malas. Mereka pintar, tetapi malas. (They are smart, but lazy.)
"Namun" and "bagaimanapun" refer to the word "however" in English. Both are used in the beginning of a (separated) sentence and is followed by comma (put before a comma) to express contrast as well. "Bagaimanapun" is rarely used in daily conversation, it is slightly more formal. On the other hand, "namun" is more commonly used. When you use these words, you need to repeat the subject once again, because it is already a new, separated sentence - just like in English. Eg: Mereka pintar. Namun, mereka malas. Mereka pintar. Bagaimanapun, mereka malas. (They are smart. However, they are lazy.)