Hey there i am looking forward to order the mjx hypergo model Makerfire so i wanted to enquire that how much duty do i have to pay in order to get it here in india

A lot most likely. Let me give you examples. The customs for my Traxxas Summit 1/10 was Rs.27,000 (I had to buy batteries and charger separately and finally including price of everything including products, delivery charges and customs, it had cost Rs.1 Lakh+). For my Axial Scx24s, each of the vehicles had cost Rs.14,000+, 4000+ for delivery and 7000+ for customs. So, I think for your 1/14 or 1/10 vehicle, the customs would be at least Rs.10,000+ (although it can vary depending on a lot of factors). In India, getting a good rc car costs you much much more than what it would to people in North America, Europe, etc.

But Brother the original cost of the rc car itself is somewhere around 12k and giving 10k just for customs is not worth it at all is there any way through which I can reduce my custom duties

If the car is only 10-12K, then customs would be less than 10K, still at least a few thousand rupees (that would vary depending on from which country is it being imported). But sadly there isn't probably a way to avoid/minimize the customs. And if you try buying one from some seller in India (i.e. if you get one to begin with), it would still be costly since they needed to pay the customs when they got it themselves and wont sell for a loss. And its not just the customs, delivery charges are significant too. We really need a proper Indian hobby grade RC car brand, but there isn't any (likely because they wont sell much in India). Customs also depend on from which country is it being imported, where are you trying to import it from?

The Parent country is china and hence ummm can I instruct the seller to decrease the bill amount in order to minimize the car's cost for example I can tell them to put 50 or 60 dollars in the invoice is it possible to decrease the custom duty with this way

Technically possible, if you dont get caught but its illegal and I dont think taking legal risks for a RC car would be worth it. Both you and the seller would likely be in legal trouble if caught, now its for you to decide....(well you and the seller).

Have you did such things before?

No, I didn't. But some people in import/export business do such things (and some end up getting caught). In my opinion, dont try that, rest is your choice.....

Nowadays customs wil use tools like google search and even google lens to identify the actual item being imported and where is it available. once they find the real cost of item they will issue the customs duty, and a fine if they find that the declared values is too low.

Which Sites can I use to get measurements/dimensions of RC plane?

But like how can i reduce the amount of custom duty its just a 1/14nth scale vehicle