I cant go in recovery mode I try the combinations and it not work I always rebooted and bypass the recovery how to fix this
You have a very vague question, but generally speaking there are a few ways to boot into recovery mode:
Most devices have a key combination that should be held down when powering on. You can find many of them on CyanogenMod's wiki. Search for your device, and if it's supported you'll usually find the instructions on the Info or Installation page. If it's not a CM-supported device, your device manual or web site may have the information, or you can look online.
From the Terminal Emulator app (available for download), you can enter the command
From a shell, if you have adb installed, you can boot into recovery with the command:
adb reboot recoverytyped from your computer.
Some ROMs (such as CyanogenMod, but others as well) allow you to select booting into the recovery from the "Shut Down/Reboot" menu in Android. You may need to enable this feature. In CyanogenMod 12, it can be enabled via the Developer options as Advanced reboot.
I believe some 3rd-party apps such as Rom Manager can also cause the device to boot into recovery mode.
If you are able to start in bootloader mode, some bootloaders will allow you to boot directly to recovery. This can be done via the UI (on a Nexus device, use the volume up/down to select the correct boot mode, then press the power button to reboot to recovery).
Finally, you can also tell the device to start the recovery on the next boot by manipulating the cache partition, but that is more advanced and I think one of the above methods will probably work for you.