Suit armhole tightness, alteration needed

[CloudLi]

I have a Canali jacket from years ago that was a tiny bit tight since beginning. Now I gained some weight, the armhole becomes very tight, especially bottom part. When I twist my torso, I can feel the bottom part of the arm hole rubbing my armpit. When I lean my shoulder forward, the back is also pulling. Can this be fixed by alterations? If so, what exactly needs to be done? I don’t think letting out waist alone would solve this