I am in the mission: "The house always win, IV". And when I completed it says that I failed a mission with caesar. If a kill mr. house then a have mission failed with mr. house. what is happening? what should I do?

That is a dummy quest than can only be failed. It's just there to tell you that you can no longers side with that faction.

This is actually supposed to happen.

With the main questline, there are 4 possible leaders, and you can only be loyal to one. once you get so far in the parth with one, it locks of the other paths.

The Ceasar misson has "failed" because of how far you've gotten with house. You'll get similar messages for the NCR at some point.

so, there is no 100% complete game, right? you should fail som mission to continue?

there is no way to continue the game without failing some missions???

Pretty much.

Because it's kinda of illogical to work for the NCR and the Legion at the same time, no?

No. There is no way to continue the game without failing some missions. It took me a while to get used to that idea too lol.

omg... very dissapoint... but ok... so much things that we miss because of this!

It encourages separate playthroughs. Your choices matter.

How is this disappointing? How do you expect to work for 4 people, all who are against each other? Thats illogical.

I thought you could do it and at the end you could choose with what party you want to fight that massive war I was expecting

I was managing it extremely well on my first playthrough believe it or not. Until I was shoehorned into Caesars questline. Obviously I would have had to pick eventually, and I had planned to pick Yes Man, but apparently I wasn't allowed to play the double agent game.

I got quite far in all of the four questlines before the game set me straight though lol.

So, if you did work for Germany and the United States in WW1 and where well-known, then you could just choose who to fight with when the time comes? I don't thinks so.

okay, okay I understand... by the way thank you for all your replies.