First you need to explain what you actually did, used a coin mixer maybe? Give us a little more information on what wallet you use, where your transactions come from, and then we can try to find out what the problem is. It may just be a problem in your wallet (not sync), so you don't see full balance, but you might also be scammed.

Edit :

This is the first time I've heard of this fake mixer - but OP is say that he is done many successful transactions, perhaps their modus operandi is to process small transactions, and then scam users when they send such big amount of coins

Sorry to hear bud, that's huge money there, but that website is scam, an that's sucks. Here's their open Scam accusation. We can't do anything regarding your funds, to get it back.

Sorry for your loss but the only chance to get them back is to contact them to their customer support. (this is less of chance)
But who knows they will give it back, you are still lucky because we can trace you BTC where it is going to landed and it seems your Bitcoin was there.

I don't think if this is a good idea, maybe you will hire a lawyer and file a case to the authorities and let the FBI hunt them. That is a huge amount of money and that kind of fraudulent must be caught.

Next time, just to make sure you have done your research in looking a good Bitcoin mixing site. (If you have enough time try to check my signature)

Sorry Mate   That amount is a sizable especially in these times when the crisis is starting to bite.

I am just curious, how did you come across this website? Maybe we could get away of trying to prevent future losses from innocent members because you are not the first person to lose money to them despite the warnings

This is the website he is talking about, they have been scamming people for sometime now

Despite making reports to google safe browsing, nothing has ever been done.

They have a profile here and have even already been tagged sometime back by DT Members. Here is one of the scam accusation threads: https://bt.irlbtc.com/view/5110697.0