Drilling through a wooden stud wall

Or onto a mounting bracket for the staircase?

Maybe you also drilled into the new Nord Stream 2 pipeline! hopefully you’re not serious about wanting to ask for advice here in the forum on whether you should continue drilling, even though you hit something with the drill in the wall. But no one can tell you for sure that you should actually continue drilling after that. There is gas, water, electricity, sewage, etc., although it could also be something simple. But you can only find that out on site. Just as info: A few months ago I drilled a mirror into the bathroom wall. In the middle of the wall, far beyond any imagination, a plumber had laid a water pipe there. Luckily I was cautious anyway because I wasn’t involved in that construction. My colleague hit an electrical line in the wall two years ago; at the time the electrician had laid several cables diagonally, apparently to save cable. Ergo: We here can’t say anything that could give you certainty in this case. Probably nothing bad would happen......probably!!!

I am also not concerned with you giving me insurance or knowing what is behind my wall. Would you rather stick to one hole and "forcefully" drill through, or drill several holes at shorter intervals until it becomes easier? In the latter case, you just have several holes in the wall.

As others have already written, it could be a beam or a metal bracket or something similar. But you simply don't know what or how strong this possible material is there, wood, metal, or whatever, which is why your question simply cannot be answered. Depending on the material and the chosen drill bit, you could drill for an hour without anything happening. In this case, I would definitely look for a spot where I can get through "easily." If the wall structure is like that, you might better look for a spot where, after an initial drill, you can then poke through with a wooden stick or something similar to the other side to make sure there's nothing in between that you better not drill into.