I'm not sure the meaning of the first part of the sentence

Question

I would like to understand the meaning of the first part of this sentence, I get parts but not the whole thing.

このままだと自分だけじゃなくてこの世界壊れるだろう。

I get that この世界壊れるだろう means this world will break.

I think まま means as it is, so このまま is something like "as this is". I don't really know about だと, I assume だ is です and と connects is to the other part of the sentence. 自分だけ means only oneself but I'm confused about じゃなくて, is this like じゃない but for some reason conjugated with くて at the end? How does that change the meaning of じゃない?

Any way, I kinda get a jist, it means something like "as this is the world will break" but I don't really know how と自分だけじゃなくて plays in . . . .

Answer 1

I believe either が or も is missing after 世界. If you're sure you've copied this sentence correctly, perhaps it's a simple typo in the original text.

このままだと自分だけじゃなくてこの世界も壊れるだろう。
If this goes on, not only me but also this world will break.

• このままだと: "If this goes on...", "At this rate...", "If nothing is done..."
  • このまま: "the same state as this/now". See this.
  • だ: "is" (copula)
  • と: conditional と. "when", "if". See this.
• 自分だけ: "only me"
• AじゃなくてB ≒ AではなくてB: "not A but B"
  • じゃ is colloquialism for では.
  • なくて is the te-form of ない. You can also use the ku-form (なく) here.
• AだけじゃなくてB ≒ AだけではなくてB ≒ AだけでなくB: "not only A but also B". See this and this.
• も: "also"
• 壊れるだろう: "... will break". Note that 壊れる is an intransitive verb and never takes を. The transitive version is 壊す.

So let's get used to this "not (only) A but (also) B" pattern, which is very useful and important!

Answer 2

You are really close, so lets try to break it down for you.

Here's your sentence:

このままだと自分だけじゃなくてこの世界壊れるだろう。

I'm going to break it down from left to right.

このままだと: このまま translates to in this state, so good job on the translation here. だ is the plain form です、so you're correct here. The と、however, is where our translations will differ. This と is actually translated to if, (see this link) so this phrase translates to something to the effect of if this is the current state.

自分だけじゃなくて: The main grammar here is found at the end, じゃなくて. You're right to say that this is a conjugation of じゃない. When ending a verb (to be in this case) with a 〜て, you give the impression that there is more to the sentence. For sake of simplicity, lets just describe this as an compound particle (and/but in particular). Really, you're creating a compound sentence. (see this link) This phrase will be something to the effect of not just me, but

世界も壊れるだろう: (notice the addition of も) This is as you translated, so I won't beat a dead horse. The whole would would break also. The also in this sentence comes from も。

So, lets translate the sentence as a whole.

If this is the current state, not just me, but the whole world will break also.

(I realize @Naruto already posted a great answer, but I figured I'd finish my answer anyway since I was already really close.)