Here's my advice for the physical challenges:
1. Index finger positioning is critical. A good place to start is to align your first knuckle with the second string. After you try that, you should hear an improvement. Adjust the vertical position of your hand up and down slightly to help with any remaining buzzes.
2. Roll your index finger on its side slightly. That puts more bone against the strings and less flesh.
3. Most of the challenge of barre chords comes from the lack of hand strength. The more you try, fail or succeed, the stronger your hand will get and your barre chords will sound better. Even if your technique is perfect, your barre chords may sound poor until you develop your hand strength. That leads me to the mental side of things....
Mental challenge:
1. Learning barre chords is a war of attrition. You have to be persistent and practice them every day to develop the hand strength you need. They will most likely sound terrible at first, but stay with it. They will gradually improve. Try not to get frustrated and discouraged. You will get it!