No, your eth holding doesnt go down with market. This has nothing to do with it. Probably, you made a transaction for eth or an erc token..and some eth was deducted as gas fees. Otherwise, there should be no reason why you Eth would go down.
Here is what I think and questions that I would like to ask....
First I see that you are in trouble and other saying that you had been hacked or what
I would say it was because of the Ethereum download of the cryptocurrency market but reading your post carefully and basing on thers post this is bad I can not help you but I can help you to prevent it again.
Now here is the question
1. Have you been using any kind of divices from the computer shop or other diveces that you use that does not beling to you?
2. Have you been doing something like downloading stuff from your own device the same time use you account to log in your device?
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If you are doing things lwhat I said above you should be careful and further for most links when you looking at the link and entering anything be sure that there is no exe at the end.
Also of you may go to youtube or Google you can search how to detect fake phishing links.