u/EffortIll1350

New to saxophone, and bought a used Opus USA tenor on Marketplace. I realized afterwards, they’re not the most trusted brand. The sax feel great and making noise was not as difficult as I thought it would be. It’s in tune with itself pretty well, but I’m struggling a lot to play the right notes in accordance with what they should sound like. The B sounds like an Ab, and the A like a Gb. Essentially every notes is incredibly flat with a piano. Is it the sax, or just me starting out. For reference, I’m using newly bought 2.5 reeds and a fresh mouthpiece