dear apple support team, I can not download numbers app on my iMac 2011(mid). I am running MacOS high sherra version 10.13.6 ...please give me the solusation.. thanks.

There is another possible alternative. Go to the Apple store and, if memory serves me, find where it displays your previous purchases. (It doesn't always do so.) If you can find that, it should allow you to download the appropriate older version for your OS. Also, if you desire to do so, you can upgrade your Mac to a newer OS.

Numbers requires Mojave 10.14 or later to run. Since you can't run Mojave, you either need to use a different app or purchase a new computer.