Nixota,
The howto at
https://www.c0ffee.net/blog/openbsd-on-a-laptop/ is very complicated and it is easy to make a mistake, for example in editing
/etc/fstab. If you make a mistake in that file, your system will not work correctly. Some things like using M:tier for updated packages are also outdated and not applicable anymore.
Just reinstall from your USB stick , say "Yes" to the question if you want to install the X Window system and everything probably will be fine.
Boot into the new system, login, gain root powers by doing
su - root and do a
# pkg_add firefoxto install Firefox.
Then as normal user in an xterm window start Firefox: [
$ firefox & and you should be able to browse the net
If you want to install more software and want to know what is available:
https://openports.pl/