Hello there!

I'm on the 4th level, but it feels strange, there's no UI whatsoever on the screen, the regular one that is there on every screen (face, hp, ammo, etc) is non-existent... is there a way to enable it somewhere? Searched for it, haven't found a thing. I'm on normal difficulty, so I don't think that's the issue. Anyone could help me with this, I'd greatly appreciate it!

Also, read the manual and ingame help, there's no reload button, is there?

Thank you guys!

Maybe you should try the "enlarge screen" key. I can't remember which one it is right now (maybe kp+), but there you have what you may need to solve your issue.
And no, there is no reload button because Duke is so though that he needs no advice in that matter.

OMG, thank you! I thought that button is for resizing the actual game window. Now, how do I marked this as "solved"?

Just seen this post and immediately I though you'd made the screen to its largest size which removes the HUD, though this answer has already been given. :)

As for marking the post as solved, well, you won't be able to with this thread as you didn't raise it as a question. The only ones who could change this are GOG support, though I doubt they'd see it as of any value to change the thread into a question. If you do want to give some recognition to javihyuga then rate their post up.

No problem, glad to help!
And now, kick some alien-bastard ass! :D