This year’s party was quieter than the last one.

We have a traditional game for the party, which is called Murder mMystery.

Even though we couldn’t understand the clues on the clue papers because it wasthey were written in English.

If you use "Even though" as the start of the sentence, you will need to follow with something opposite in nature.
For example, "Even though we couldn’t understand the clues on the clue papers because they were written in English, we could guess what they meant by the pictures on them."

We only could donly walking around other people.

In case this was meant to be the follow up for the "even though", you would not say "only" as that will make it negative in nature similar to the first part of the sentence.
"Even though we couldn’t understand the clues on the clue papers because they were written in English, we could walk around other people"

Everyone was very passionated and some of the groups had already figured out some keywords.

"had" is used here to maintain the same time frame (the past) as the "was", and the "already figured out" part tell us that it happened even before that time.

Unfortunately, we leaved fromft the office before the murderer willas revealed.

I wondered about the story of the game.

Maybe, next year, I couldan enjoy it. (or Maybe next year, I will enjoy it.)

Holiday pParty

I'm correcting with proper title capitalization, but for something casual like a post, the original is fine too.

I participated in a holiday party this evening.

We have a tradition game for the partygame we play for the party as a tradition, which is Ma murder mystery.

Even though wWe couldn’t understand the clue papers because it was written in English.

"Even though" implies a contrast between not understanding the clue and it being super difficult, but there's no contrast.

We onlyAll we could do was walking around people to observand observe people.

Everyone was very passionated and some of the groups had already figured out important keywords.

Unfortunately, we leaved fromft the office before the murderer willas revealed.

I wcondertemplated the story of the game.

"contemplated" sounds more natural here. "I thought about the story of the game" is another option too.

If I had better English skills, I would've enjoyed the game.