You need about two weeks for radiation levels to drop. Ideally you are underground or have several walls and air filtering between you and contaminated regions.
Past that, food becomes a meaningful issue since your topsoil is quite irradiated.
You will probably have a shorter lifespan by a decade or so but obviously much longer than perishing immediately.
You will almost certainly die either in the first few minutes, or in the first few weeks following nuclear war, because our society is built on a house of cards of global supply chains, which will all go directly, and irreversibly (at least, within timelines that will matter to your survival) straight to shit.
Some of the architects of the war might survive in their hardened bunkers, if they are out of the way enough. I'm of a mind that they should not be allowed to outlive their constituents, but this does not seem to be a popular opinion.
Sounds like my brick and wooden basement is not going to work. Also the air filtering is not good enough. I guess the real chance is to learn survival, live far away from cities, preferably close to mountains and try to live by hunting for two weeks? Guess I can also keep a vehicle and some gas too after those two weeks. Anything more would need a proper shelter.
Just make sure the air situation is sorted. You really don't want to leave cover during that time. Two weeks is not a lot of food to stock.
Even experienced hunters have bad days. Hunting requires cooking and hunting is a riskier activity for injury. Nobody is around immediately post nuke to sew you back together.
Air filtering is partially helped by the fact that most people nowadays have some supply of good masks, which can ensure that any radioactive dust stays outside of you instead of giving you lung cancer.
Past that, food becomes a meaningful issue since your topsoil is quite irradiated.
You will probably have a shorter lifespan by a decade or so but obviously much longer than perishing immediately.