How to give a player the ability to fly?

I made a script for flying but it doesn't work. If I loop the part that lifts up the player, the player falls down to the ground after lifting by 1/5 of a stud. If I put multiple together it will lift the player a higher. I don't understand why repetition of the line lifts up the player, but a loop won't lift them up. Can someone tell me what I am doing wrong to try and give the player flying abilities. One more problem is the player will always turn to a certain direction whenever I hold space to try and fly. I know it has something to do with how I'm trying to fly, but I don't know what since I don't usually work with CFrames. Here's is the code