you can't teach old dog new tricks 老狗学不了新把戏；老狗学不来新花样

【例句】
You can't teach old dog new tricks.It will bee easier to give up.
老狗学不了新把戏。放弃比较容易。

There is a saying which goes, "You cannot teach an old dog new tricks. "
有句俗话说：“老狗学不来新花样。”