My iphone got security lockout mode. How to enable without loosing the data.

You will need to restore the device using a computer. The process will erase the device. Later you can restore your data from a recent back-up. Instructions here…

If you forgot your iPhone passcode - Apple Support

You are learning the importance of a good back-up plan. Many of us learned the hard way!

You don’t. Your only option is to erase it and restore. Anything that was not backed up or synced to the cloud is gone.