Install TWRP on encrypted device

I would like to install TWRP on an encrypted device to make a backup and maybe reinstall firmware. (Samsung SMT-530) The reason I wanna do this is because when restarting, I am able to enter password to decrypt but will get stuck in subsequent samsung logo screen forever, without giving me chance to unlock device. And after some googleing the solution seems to be installing twrp and update firmware. The source for this solution says clearly that doing so will wipe out the device, and recommends to backup first. And I thought, and this probably will sound silly, I could make a backup via TWRP. When trying to go into recovery mode, and install TWRP from sd card gives the following errors. First screenshot is after going into recovery mode, second is error messages after trying to install twrp from sd card Most probably this is a silly question, but could please anyone tell me whether it is possible to install TWRP recovery and make a complete backup without having to wipe out - Factory Reset my device ? USB debugging is off device is unrooted and have tried to find clear info via google without success.