evenとat allの訳し方がわかりません。。

文の一部だけを抜き出して訳してみろと言われましても普通は無理ですよ。
原文は次のようになっていますので、「面白い動画を見せてあげようと言われたグループは、実際に面白い場面に進む前にすでにアドレナリンとコルティゾールのレベルが下がってしまった」という意味になります:

In fact, the researchers found that simply learning they would watch something funny decreased the men's stress hormone levels. Half the men in the experiment were told they would watch funny videos, while the other half were told they would sit in a room with magazines. The group who got to watch funny videos had 70% lower adrenaline and 39% lower cortisol before they had even watched anything funny at all.
https://eikaiwa.dmm.com/app/lessons/humor-and-health-3-good-reasons-to-laugh-more/b-9YYIIFEeuY5Fvw8tESxw