'He is poor but honest.' _ in this sentence which is conjunction?

I have read the book _ you lent me. Tell me _ that. He could not win but learnt a lot. Which parts of speech is the word 'but'? The children studied in a class room _ windows were never opened. Give her a telephone number to ring ……… she gets lost. Visit you — I have finished my homework. Look before you leap. The word before used in the sentence is— Water boils _ you heat it to 100° centigrade. The main objective of a 'conjunction' is- I will watch while you sleep. এখানে “while শব্দটি-