最近外食し過ぎてるんだよ。
I have been (eating out, dining out) too often lately.
外食をするを英語では"eat out"や"dine out"と言います。
ex, "Mom, I don't need dinner tonight. I'm going to eat out with my friends."
「お母さん、今夜は夕飯いらないから。友達と外で食べてくる。」
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冗談はさておき、夕食の件はごめんね。
(All joking aside, All kidding aside), I'm sorry about dinner.
「冗談はさておき」を英語でいうと"all joking aside"や"all kidding aside"と言います。
誰かと会った時場を和ませるため冗談などを交わしますよね。
そこから本題に入りたい時など、切り替えしに"all joking aside..."とよく言います。ビジネスの場などでも便利に使えます。
【冠詞について】
"at the dinner" vs "at dinner"
You don't need "the" in this situation. Although you can also write the sentence with "the" the nuance is slightly different. If you say "I'm sorry about the dinner" it sounds as if you had somehow ruined a dinner that you went to with the other person. If you say "I'm sorry about dinner" it sounds like you were not able to make it to a dinner that you had scheduled with another person (canceled or something like that), although it could also be used if you had somehow ruined dinner. So I suppose it depends a little on what you want to say. I thought the second situation was more common and could be used in both situations.
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あとで埋め合わせするからね。
I'll (make it up) to you later.
約束をしていたけれどどうしても行けなくなってしまう時などありますね！その時「後で埋め合わせをするから！」と言う時があると思います。
誰かに埋め合わせをすると言う時は英語で、"make it up to+人"と言います。
ex. "I will make it up to you so please trade shifts with me."
「埋め合わせをするからシフトを交換して！」
