Assalamualaikum, I am actually a 14 year old boy, my family goes to dargah (shrine of a dead person) and I don't know exactly what they do but I think they might have committed shirk, I realised this all is haram and I repented from it, only Allah knows whether my repentance would be accepted or not and I am sure the next time I go to a dargah, I would try to avoid it but if I can't, I'll don't do anything there or just do acting, but my family does it, I am the youngest In my family so they may not listen to what I am saying. How can I get my family to not go to dargah?
You don't need to try to stop them from visiting the grave of a believer. In fact, visiting the cemetery has many benefits, such as increasing remembrance of death, and can even be a recommendable practice.
You do not know whether your family has committed shirk (ie. treating anything other than Allah as being a partner of His or independent of Him). Don't rush to assume that they have; it is better to hold a good opinion of fellow believers and make excuses for them before jumping to the conclusion that they have sinned.
It's good that you care for your family; you must love them a lot. It's also clear that you really want to worship Allah exclusively and sincerely. Focus on being kind and respectful to your family, and make them happy with you, as Allah has commanded. In doing so, you will both be obedient to Allah as well as caring for the ones you love.