metal brake lines

It's a brand new cylinder. And I didn't mean caliper earlier lol. I replaced the lines the first time as I need to drive it home and no brakes. So I went to replace the rubber lines and the metal ones didn't come free at the rubber line side so I replaced them too. The pass side I had to buy three lines and the driver side went on no prob. Now the cylinder acted up and I replaced it and I knew the one I had replaced was gonna give me issues again, sure enough it did. So I bought 2 new lines cause I bought a cylinder for the driver side to replace next time I want to work on the car. Both failed me on the passenger side again, and I'm like wtf, you metal lines hate me lmao although I'm not really laughing too much. So here I am needing to go out and get another line. I would dick with em and try to get it to seal better but last time I sat there a good two hours and not working so ya no more. If it doesn't work and I play with it a bit then it just ain't working, or so that's how I feel