Hi i kinda joined the vampires by ''mistake'' and i became a warewolf to cure myself again but then i couldn't join dawnguard cause they kinda killed me when i did show upp i have only made a few missions on vampire plz help i want to join dawnguard and excuse my bad english plz help

You can't. After you join the vampires there's no turning back - the Dawnguard will always kill you on sight. To join them, you'd have to start over.

this tells you pretty much all

Load a previous save? This is the reason why I keep multiple "milestone" saves so I can always start up from the end of my last questline and the start of my next.