I'm afraid we are completely sold out for this week, so we aren't taking any more reservations now.
We aren't accepting any more reservations for this week, because we've sold out.
ご質問ありがとうございます。
① "I'm afraid we are completely sold out for this week,"＝「すみませんが、今週分は完売しました。」
"so we aren't taking any more reservations now."＝「今はもう予約を受け付けていません。」
② "We aren't accepting any more reservations for this week,"＝「今週分の予約はもう受け付けていません」
"because we've sold out."＝「なぜかというと、完売したので。」
ご参考に。
アメリカ合衆国 
