I was trying to log into my Web Vault but I pressed so quickly on this result from Bing and it seems to be fake, because the official vault has to be vault.bitwarden.com, unless this is an old version. Of course when I pressed log in it displayed the “Unexpected error” message. Should I worry now about my MP?
web-vault.bitwarden.com is still under the bitwarden.com top-level domain. If you went to some variation where the TLD part .bitwarden.com wasn’t exactly that than, yes, that would be bogus.
That said, web-vault.bitwarden.com appears to be an alias. No idea of it’s purposes, but it resolves to BW servers same as vault.bitwarden.com. And since it is within their top-level domain you’d likely be fine.
Are you certain it was *.bitwarden.com and not something else that looked really similar like web.vault-bitwarden.com or something? (I made that one up, btw).
There have been fake entries showing up in search engines for well known services (and BW is certainly no exception). It’s wise to be careful what you click on without looking closely.
Or better yet, follow your own bookmarks. 
Hi @thomrnowtea and welcome to the Community!
In general, if you enter your credentials in a bogus site, you should change your MP immediately and make certain 2FA is turned on.
Do you already have 2FA turned on?
Thanks all doublechecking on this one, for now, use https://vault.bitwarden.com/ which is accessible from the main Bitwarden page.