[jggimi]

You can reach a shell in single-user mode. That means you might be able to learn what is causing the problem. Kernel messages are stored in a looping buffer in RAM, and can be examined with the dmesg(8) command. So something like # dmesg | less will help you page through the buffer until you hopefully see an error message followed by the reboot. If there is an error message, it should give us (and you) a hint at what may be causing the reboot loop.

Answering "y" or "F" to fsck_ffs(8) prompts to force the deletion or the "fixing" of files in error on the filesystem will cause unrecoverable data loss. What that loss means to the OS and applications will depend on exactly what was lost. I can't tell from what's been posted so far if critical data loss is the root cause of your current problem.

As a brand-new user who stated here that OpenBSD partitioning and sector allocation confuses you, permitting the system to install with the default automatic filesystems layout may help prevent some types of mistakes that might arise when new users manually provision storage. The OpenBSD recommended partitioning schema also improves security and has other advantages, as outlined in the FAQ. Should this problem end up not being recoverable and require a re-install, please consider using OpenBSD's automatic allocation until you've gained a little more experience with the OS.