I am going to take a slightly different tact here since I (also a newbie here) come from a different (not better, not worse, just different) school that many of the folks here. And I have been known to go into old structures like this specifically to shoot graffiti.
In the first image, it looks to me like your intent was to focus on the "The Tunnels Are Cursed" moreso that to depict the inside of the bunker. In other words, it appears to me (and this is your image and your vision) to be a modern-day graffiti image more than a historic army bunker shot.
Using your phone as a torch is good improvisation but obviously not ideal. It has resulted (or was it the processing) in somewhat of a pinhole camera look to that first image. Again, if that was your objective, fine. But if it wasn't, I would have considered a much longer exposure. I don't know but say maybe 5 minutes or even longer using your bulb setting. That could have picked up more detail in the shadows. Then, if my objective was to highlight the graffiti, I would have vignetted the image at low opacity to darken the area surrounding the "The Tunnels Are Cursed" thereby drawing the eye straight in where I want to to go. But again, that's me. This is your image based on your vision. We must not lose sight of that.
Quite honestly the second image, while better lit, is more problematical to me. It seems to lack a focal point so my eye just drifts around the image looking for a place to rest and finds none. There is no single piece of graffiti to hold my attention. The stone work is not sharp enough, structured enough to do it. The "X" timbers could but they are placed in such a way as to appear an afterthought. Just my two cents on that one.
I'd like to hear your thought and opinions.
Regards,
Ed Vatza
Ed Vatza Photography
www.edvatza.com