Denis,
it's always nice to be of some help - I've gotten a lot of help here myself!

The red button at the back of the enlarger head is used for extra filtration. The fuse is in the transformer, the big heavy thing between the enlarger and the wall plug.

The two bigger knobs on the underside of the head is for getting off the enlarger head itself. Just unscrew them to loosen the head, lift it upwards to go free of the screws and turn it upside down and there you can see the halogen bulb.

The bulb is taken out by bending a bit on the metal lips and slowly lifting it upwards at the same time. Don't put any fingers on the bulb itself - that will ruin the bulb. I use cotton gloves when I change it. Probably overkill, but better safe than sorry. Detach the cable from the bulb, and now you know how to replace the halogen light - just do it in reverse!

The smaller screw in the center is for restitution, which means that you can correct a tilting horizon to be straight, or a tall house to not "fall over" in a photograph. I've never done this, so I can't be more of help regarding that. Experiment. Or do a search here in the APUG archives.

Let me know if you sort out the problem with the short exposure times.

Regards,
J