#1
I'm a beginner who have just been playing for about 5 months.

Yesterday, why I was practicing, my high E broke and I decided to change the whole set of strings as they were pretty old. So when I have changed all and tuned the guitar up, I have fret buzz at the open low E, it buzzes against the first fret, this problem did not exist before. How can I fix it ? Please help

My guitar is a Gio Ibanez GRX90 without a double locking bridge.
#2
a fret buzz at the first fret is a sign of a worn down nut, check to see what kinda gap you have between the string and the first fret when you're not touching the string.
It's also possible, especially if you changed to a smaller gauge string, that your neck is too straight or even backbowed a little. Fret the first and 15th fret of yoru Low E and look at the gap at the 7th fret.