I was playing my classical guitar yesterday and noticed that whenever I played any string on the first fret, it would like sound dead, idk what’s going on, I’m new to this. Any help would be appreciated :)
From your description the most probable cause is that the second fret is higher than the first fret and blocking the strings from vibrating freely. This can be caused by the first fret being too low compared to the other frets or the second fret installed too high or coming out of the fret slot.
It is also possible that your action is too low on the entire guitar. If it only has the problem with the first fret and not any other fret up the neck, then it a problem with those first two frets. If your strings are buzzing or having problems voicing up the neck then your action may be too low at the bridge.
While you can examine the guitar and make some modifications yourself depending on your comfort level with tools, the easiest thing to do would be to take it to a Luthier or qualified guitar tech and have it evaluated for an action adjustment or fret level.