Problem when booting to twrp recovery

Hello, some days ago I tried to root my huawei p9 lite vns-l31.
First I unlocked the bootloader without a problem.
Then I tried to flash a twrp recovery and the command prompt said it was succesfull but when I try to boot in recovery it is stuck on the following screen:
"Your device has been unlocked and can't be trusted. To learn more visit: - some url - Your device is booting now...".
Holding the power button makes the phone go off en rebooting to the same screen. Power button without volume up or down has no affect.
I can only use the phone again when the battery is empty and I recharge.

Some thing to notice during my procedure:
-when I type "adb devices" it says:
adb server version (31) doesn't match this client (39). killing server... and than it started daemon en showed my device.
-when I do "fastboot reboot" it says "remote: not allowed". So I tried powering to recovery with power button and volume down and afterwards with a chinese huawei program.

Has anyone a solutions to this problem or any advice/tips?