I used to be like that. I couldn’t get above 75 kg no matter how much I lifted or ate protein and stuff. This solved itself by getting older. Now I still have

I used to be like that. I couldn’t get above 75 kg no matter how much I lifted or ate protein and stuff. This solved itself by getting older. Now I still have trouble putting on muscle but getting fat is quite easy :-). In hindsight I think it’s not a good goal to gain weight if your body doesn’t respond. I would focus on eating right and being strong, flexible and coordinated and let the weight settle wherever it wants.