Soft Bricked (Locked / S-Off / Recovery broken?)

Hey guys!
I really hope anyone can help me out with this.

So, today I thought "Why not upgrading to 5.1 and unbranding it?". I followed a tutorial on a german android forum to unbrand it.
But I was unlocked and rooted so I had to return the changes in order to update it. I changed the CID to HTC__102, made it S-ON again and even locked it, then tried flashing a non branded european RUU via my microSD card, which somehow failed and I ended up having a bootloop. So I upgraded my firmware aswell to 2.10.401.1 but now the recovery is not even working :( i only get a red triangle, which might be a common problem with 5.1 on our M9, as I read later on.

Download mode, fastboot etc is working fine
edit: stock recovery is working as well

Can anybody help me get my M9 going again?
I thought about try another flash with a unlocked ROM via microSD card but I'm not sure which one as the one I mentioned failed.

Here are some more details about my current situation:

Quote:

(bootloader) kernel: lk (bootloader) product: htc_himauhl (bootloader) version: 1.0 (bootloader) imei: 357226062454459 (bootloader) version-main: 2.10.401.1 (bootloader) boot-mode: download (bootloader) version-baseband: 01.04_U11440601_71.02.50709G_F (bootloader) version-bootloader: 1.0.0.0000 (bootloader) mid: 0PJA10000 (bootloader) cid: HTC__102

edit: In another thread I read how to boot into the stock recovery and it's working. But still not booting