Pelvic exercises. They do help but you need to be consistent with them for a while. Basically strengthening the muscles behind your dick which keep the blood in.

The only short term solutions are Viagra and Cialis, or the more generic stuff you can order online like Sildenafil. Relying on drugs isn't great though, obviously.

I had trouble with this kind of stuff too man. It sucks. A lot of it is mental. You get inside your own head. I was open with my partner at the time and she was understanding. It may have helped that I got really good at eating pussy.

The best advice is a healthier lifestyle. Including mental health like quitting porn, which isn't easy with a lot of time online. Also reducing smoking and alcohol.

For dietary things, I don't know for absolute sure if these work but they always showed up whenever I would look into it:

Daily multivitamin, especially with magnesium and vit. B6

Fresh watermelon, avocado, apples, walnuts and almonds. Pretty cheap in most places. I would basically have 5-6 slices of each in a pot and also eat a small bag of mixed nuts with different coatings every day so it didn't get boring. I called it Sex Mex.

Ashwaganda tea. I'm British so I was already drinking tea every evening I just changed to this stuff. It's on Amazon.

Chicken and fish also showed up a lot.

Basically this is just healthy eating, but these things in particular seemed to be on every website and recommendation I saw. It's really easy to work them into your diet. Also do some light exercise, even just sit-ups and kegels before bed. And definitely reduce porn.

Sexual health is part of general health. Best of luck man.