YOU SAID:

i got to walk in a party and have a seat

INTO JAPANESE

私はパーティーに参加して席に着かなければなりません

BACK INTO ENGLISH

I have to join the party and take a seat

INTO JAPANESE

パーティーに参加して席に着かなければなりません

BACK INTO ENGLISH

You must attend the party and have a seat

INTO JAPANESE

あなたはパーティーに出席して席を確保しなければなりません

BACK INTO ENGLISH

you must attend the party to secure a seat

INTO JAPANESE

席を確保するにはパーティーに出席しなければなりません

BACK INTO ENGLISH

You must attend the party to secure your seat

INTO JAPANESE

席を確保するにはパーティーに出席する必要があります

BACK INTO ENGLISH

You must be at the party to get a seat

INTO JAPANESE

席を確保するにはパーティーに行かなければなりません

BACK INTO ENGLISH

you have to go to the party to get a seat

INTO JAPANESE

席を確保するにはパーティーに行かなければなりません

BACK INTO ENGLISH

you have to go to the party to get a seat