Please tell me that what should we do when our parents are forcing us to do things that are not allowed in Islam like

1. gold ring for men
2. whole mehndi event
3. jahaiz

And when we rebel they just put this " duniya hy krna prta hy" statement infront of us. What should I as a child who is getting married and do not support all this?

by

1) Yes gold ring is haram for man. Tell them to give Aqeeq ring which is recommended also.

2) Now Mehendi no doubt is not in Islam but if there are only female then it is not haram.

3) Yes if groom or groom family demand it is not jayez but if from their own will if they are giving some gift or exchange of gift from both side, it is jayez.

Only one thing is against the shariah is Gold ring for groom which is Haram but try to resolve this issue patiently with wisdom.
As you mentioned above when we rebel my dear sister, rebel itself is not a good thing rather with respect try to resolve gently
Actually in Isam wajib is Nikah and Mehr and Mustahab is waleema
Rest is cultural.
Better you involve elders of the family and local scholar In’Sha’Allah I’m sure it is not a big issue they will understand
Our sincere prayers are with you and your parents and marital life.