Keep up the good luck!
いいぞその調子!
keep up with ...
…に遅れないでいる
keep up with the pace of change
変化の速度について行く
keep up with the payments
期日に遅れないように支払う
keep watch (on ...)
(…の)見張りをする
keep within one's (proper) sphere
本領[本分]を守る
Keep your back straight at all times.
常に背筋を伸ばしていなさい
Keep your chin up!=Chin up!
((略式))がっかりするな,元気を出せ
Keep your elbows off the table.
テーブルにひじをつくな
Keep your grubby hands [paws] to yourself!
ちょっかいを出すな