User blog:Mgf60/Vol.3 Ch.122: Naver Endnote Explanation

The original korean: 나도 못갔는데 네가 먼저는 안되지.

나도: "나" is the root pronoun "I" with the suffix "-도" meaning "Also/as well", so it is "I also".

못갔는데: "갔" is the root verb meaning "Gone (Past tense of to go)", with the affix being "못-" meaning "cannot/not", and the connective suffix "-는데" is used between two separate but related statements where one leads to the other in some way, like "[even] though/but/so/therefore/and", which gives the meaning of "[I] cannot have gone, so...".

The first clause of the sentence when combined and the grammar is adjusted gives "I could not go either, so...".

네가: "네" is the root pronoun "You" when combined with the subject particle "-가", meaning the subject of the sentence is "You".

먼저는: "먼저" is the root adverb "first" with the topic particle "-는" added to the end, meaning the topic of the sentence is "[being] first".

안되지: "안되" is the root verb "to fail" with the suffix "-지", which in this case is used to do a long negation from the subject "you" to the verb "to fail", with long negation meaning that the entire clause (as determined by the subject particle) is negated. This turns "you are the first the fail" into "you are not the first to fail". When dealing with negative verbs long negation is used almost exclusively, since simple negation would just leave you with the positive equivalent of the verb, like fail would turn into succeed.

When the long negation is accounted for it creates the clause "...you are not the first to fail".

This makes the sentence: "I couldn't go either, so you are not the first to fail.".