I want to know if it's safe to buy Bitcoin without having the basic knowledge of it ?
never ever do that! Bitcoin is an ultra-volatile asset so it is very important that the investor understands that risk. You can surely guide him on buying bitcoin, using a wallet, etc. But you must not hold his bitcoin in your wallet at any cost. If I were you, I wouldn't do it! But yes, I will share my honest opinion about bitcoin and other related services with that person just to help him find a suitable way. The decision must come from the other person and he can base his decision on my input. But I wouldn't take the risk to do things on his behalf.